ADDED   SRM/550-U/1C.cpp
Index: SRM/550-U/1C.cpp
==================================================================
--- SRM/550-U/1C.cpp
+++ SRM/550-U/1C.cpp
@@ -0,0 +1,198 @@
+#include <iostream>
+#include <sstream>
+#include <iomanip>
+#include <vector>
+#include <string>
+#include <map>
+#include <set>
+#include <algorithm>
+#include <numeric>
+#include <iterator>
+#include <functional>
+#include <complex>
+#include <queue>
+#include <stack>
+#include <cmath>
+#include <cassert>
+using namespace std;
+typedef long long LL;
+typedef long double LD;
+typedef complex<LD> CMP;
+
+static const int MODVAL = 1000000007;
+struct mint
+{
+	int val;
+	mint():val(0){}
+	mint(int    x):val(x%MODVAL) {}
+	mint(size_t x):val(x%MODVAL) {}
+	mint(LL     x):val(x%MODVAL) {}
+};
+mint& operator+=(mint& x, mint y) { return x = x.val+y.val; }
+mint& operator*=(mint& x, mint y) { return x = LL(x.val)*y.val; }
+mint operator+(mint x, mint y) { return x+=y; }
+mint operator*(mint x, mint y) { return x*=y; }
+
+template<typename T>
+vector<T> MATMUL(const vector< vector<T> >& a, const vector<T>& v)
+{
+	int N = a.size();
+	vector<T> u(N);
+	for(int i=0; i<N; ++i)
+	for(int j=0; j<N; ++j)
+		u[i] += a[i][j]*v[j];
+	return u;
+}
+
+template<typename T>
+vector< vector<T> > MATMUL(const vector< vector<T> >& a, const vector< vector<T> >& b)
+{
+	int N = a.size();
+	vector< vector<T> > c(N, vector<T>(N));
+	for(int i=0; i<N; ++i)
+	for(int j=0; j<N; ++j)
+	for(int k=0; k<N; ++k)
+		c[i][j] += a[i][k]*b[k][j];
+	return c;
+}
+
+template<typename T>
+vector< vector<T> > MATPOW(vector< vector<T> > a, LL e)
+{
+	int N = a.size();
+	vector< vector<T> > c(N, vector<T>(N));
+	for(int i=0; i<N; ++i) c[i][i] = 1;
+	for(; e; e>>=1) {
+		if(e&1)
+			c = MATMUL(c, a);
+		a = MATMUL(a, a);
+	}
+	return c;
+}
+
+class ConversionMachine { public:
+	int countAll(string word1, string word2, vector <int> costs, int maxCost)
+	{
+		int d[3] = {};
+		LL minCost = 0;
+		for(int i=0; i<word1.size(); ++i) {
+			int dd=0;
+			while( word1[i] != word2[i] ) {
+				dd      += 1;
+				minCost += costs[word1[i]-'a'];
+				word1[i] = (word1[i]+1-'a')%3 + 'a';
+			}
+			d[dd] += 1;
+		}
+
+		if( minCost > maxCost )
+			return 0;
+		LL c3 = accumulate(costs.begin(), costs.end(), 0LL);
+		return solve(d, (maxCost-minCost)/c3*3+d[1]*1+d[2]*2).val;
+	}
+
+	mint solve(int d[3], int rem)
+	{
+		int n = d[0]+d[1]+d[2];
+
+		map<pair<int,int>, int> enc;
+		for(int b=0,id=0; b<=n; ++b)
+		for(int c=0; b+c<=n; ++c,++id)
+			enc[make_pair(b,c)] = id;
+		int D = enc.size();
+
+		vector< vector<mint> > M(D+1, vector<mint>(D+1));
+		for(int b=0; b<=n; ++b)
+		for(int c=0; b+c<=n; ++c)
+		{
+			int a = n-b-c;
+			if(a) {
+				M[enc[make_pair(b,c+1)]][enc[make_pair(b,c)]] = a;
+			}
+			if(b) {
+				M[enc[make_pair(b-1,c)]][enc[make_pair(b,c)]] = b;
+				if(b-1==0 && c==0)
+					M.back()[enc[make_pair(b,c)]] = b;
+			}
+			if(c) {
+				M[enc[make_pair(b+1,c-1)]][enc[make_pair(b,c)]] = c;
+			}
+		}
+		M.back().back() = 1;
+
+		vector<mint> V(D+1);
+		V[enc[make_pair(d[1],d[2])]] = 1;
+		V.back() = V[0];
+
+		return MATMUL(MATPOW(M, rem), V).back();
+	}
+};
+
+// BEGIN CUT HERE
+#include <ctime>
+double start_time; string timer()
+ { ostringstream os; os << " (" << int((clock()-start_time)/CLOCKS_PER_SEC*1000) << " msec)"; return os.str(); }
+template<typename T> ostream& operator<<(ostream& os, const vector<T>& v)
+ { os << "{ ";
+   for(typename vector<T>::const_iterator it=v.begin(); it!=v.end(); ++it)
+   os << '\"' << *it << '\"' << (it+1==v.end() ? "" : ", "); os << " }"; return os; }
+void verify_case(const int& Expected, const int& Received) {
+ bool ok = (Expected == Received);
+ if(ok) cerr << "PASSED" << timer() << endl;  else { cerr << "FAILED" << timer() << endl;
+ cerr << "\to: \"" << Expected << '\"' << endl << "\tx: \"" << Received << '\"' << endl; } }
+#define CASE(N) {cerr << "Test Case #" << N << "..." << flush; start_time=clock();
+#define END	 verify_case(_, ConversionMachine().countAll(word1, word2, costs, maxCost));}
+int main(){
+
+CASE(0)
+	string word1 = "a"; 
+	string word2 = "b"; 
+	int costs_[] = {100,2,3};
+	  vector <int> costs(costs_, costs_+sizeof(costs_)/sizeof(*costs_)); 
+	int maxCost = 205; 
+	int _ = 2; 
+END
+CASE(1)
+	string word1 = "abcba"; 
+	string word2 = "abcba"; 
+	int costs_[] = {67,23,43};
+	  vector <int> costs(costs_, costs_+sizeof(costs_)/sizeof(*costs_)); 
+	int maxCost = 0; 
+	int _ = 1; 
+END
+CASE(2)
+	string word1 = "cccccccc"; 
+	string word2 = "aaaaaaaa"; 
+	int costs_[] = {10000000,1,1};
+	  vector <int> costs(costs_, costs_+sizeof(costs_)/sizeof(*costs_)); 
+	int maxCost = 100; 
+	int _ = 40320; 
+END
+CASE(3)
+	string word1 = "aa"; 
+	string word2 = "cc"; 
+	int costs_[] = {1,10,100};
+	  vector <int> costs(costs_, costs_+sizeof(costs_)/sizeof(*costs_)); 
+	int maxCost = 1787; 
+	int _ = 123611681; 
+END
+/*
+CASE(4)
+	string word1 = ; 
+	string word2 = ; 
+	int costs_[] = ;
+	  vector <int> costs(costs_, costs_+sizeof(costs_)/sizeof(*costs_)); 
+	int maxCost = ; 
+	int _ = ; 
+END
+CASE(5)
+	string word1 = ; 
+	string word2 = ; 
+	int costs_[] = ;
+	  vector <int> costs(costs_, costs_+sizeof(costs_)/sizeof(*costs_)); 
+	int maxCost = ; 
+	int _ = ; 
+END
+*/
+}
+// END CUT HERE

Index: lib/numeric/modArith.cpp
==================================================================
--- lib/numeric/modArith.cpp
+++ lib/numeric/modArith.cpp
@@ -36,10 +36,47 @@
 		for(int kk=1; kk<nn; ++kk)
 			CP_[nn][kk] = CP_[nn-1][kk-1] + CP_[nn-1][kk];
 	}
 	return k<0 || n<k ? 0 : CP_[n][k];
 }
+
+template<typename T>
+vector<T> MATMUL(const vector< vector<T> >& a, const vector<T>& v)
+{
+	int N = a.size();
+	vector<T> u(N);
+	for(int i=0; i<N; ++i)
+	for(int j=0; j<N; ++j)
+		u[i] += a[i][j]*v[j];
+	return u;
+}
+
+template<typename T>
+vector< vector<T> > MATMUL(const vector< vector<T> >& a, const vector< vector<T> >& b)
+{
+	int N = a.size();
+	vector< vector<T> > c(N, vector<T>(N));
+	for(int i=0; i<N; ++i)
+	for(int j=0; j<N; ++j)
+	for(int k=0; k<N; ++k)
+		c[i][j] += a[i][k]*b[k][j];
+	return c;
+}
+
+template<typename T>
+vector< vector<T> > MATPOW(vector< vector<T> > a, LL e)
+{
+	int N = a.size();
+	vector< vector<T> > c(N, vector<T>(N));
+	for(int i=0; i<N; ++i) c[i][i] = 1;
+	for(; e; e>>=1) {
+		if(e&1)
+			c = MATMUL(c, a);
+		a = MATMUL(a, a);
+	}
+	return c;
+}
 
 /*
 // MODVAL must be a prime!!
 LL GSS(LL k, LL b, LL e) // k^b + k^b+1 + ... + k^e
 {
@@ -46,30 +83,10 @@
 	if( b >  e ) return 0;
 	if( k <= 1 ) return k*(e-b+1);
 	return DIV(SUB(POW(k, e+1), POW(k,b)), k-1);
 }
 
-LL Cpascal(LL n, LL k)
-{
-	vector< vector<LL> > c(n+1, vector<LL>(k+1));
-	for(LL nn=1; nn<=n; ++nn)
-		for(LL kk=0; kk<=min(nn,k); ++kk)
-			c[nn][kk] = kk==0 || kk==nn ? 1 : ADD(c[nn-1][kk-1], c[nn-1][kk]);
-	return c[n][k];
-}
-
-vector< vector<LL> > MATMUL(vector< vector<LL> >& a, vector< vector<LL> >& b)
-{
-   int N = a.size();
-   vector< vector<LL> > c(N, vector<LL>(N));
-   for(int i=0; i<N; ++i)
-   for(int j=0; j<N; ++j)
-   for(int k=0; k<N; ++k)
-      c[i][j] = ADD(c[i][j], MUL(a[i][k],b[k][j]));
-   return c;
-}
-
 // works for non-prime MODVAL
 LL GEO(LL x_, LL e) // x^0 + x^1 + ... + x^e-1
 {
    vector< vector<LL> > v(2, vector<LL>(2));
    vector< vector<LL> > x(2, vector<LL>(2));