#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;
class CrossingTheRiver { public:
string isItEvenPossible(int waterWidth, int landWidth, vector <int> blockHeight, int depth)
{
return solve(waterWidth, landWidth, blockHeight, depth) ? "POSSIBLE" : "IMPOSSIBLE";
}
bool solve(int WW, int LW, vector<int> B, int D)
{
if( count(B.begin(), B.end(), D) >= WW )
return true;
sort(B.begin(), B.end());
for(int lastW=D; lastW<=D+WW; ++lastW)
for(int lastL=lastW-D; lastL<=lastW-D+LW; ++lastL)
if( solve2(B, WW, D, lastW, LW, lastW-D, lastL) )
return true;
return false;
}
bool solve2(vector<int> B, int WW, int W_min, int W_max, int LW, int L_min, int L_max)
{
for(int h=W_min+1; h<=W_max; ++h,--WW)
if(!erase(B, h))
return false;
for(int h=L_min+1; h<=L_max; ++h,--LW)
if(!erase(B, h))
return false;
int both = 0;
for(int i=0; i<B.size(); ++i)
if( W_min<=B[i] && B[i]<=W_max && L_min<=B[i] && B[i]<=L_max )
both++;
else if( W_min<=B[i] && B[i]<=W_max )
--WW;
else if( L_min<=B[i] && B[i]<=L_max )
--LW;
return (max(WW,0)+max(LW,0) <= both);
}
bool erase(vector<int>& v, int n)
{
vector<int>::iterator it = find(v.begin(), v.end(), n);
if( it == v.end() )
return false;
v.erase(it);
return true;
}
};
// 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 string& Expected, const string& 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(_, CrossingTheRiver().isItEvenPossible(waterWidth, landWidth, blockHeight, depth));}
int main(){
CASE(0)
int waterWidth = 3;
int landWidth = 3;
int blockHeight_[] = {3,4,4,5,5, 6};
vector <int> blockHeight(blockHeight_, blockHeight_+sizeof(blockHeight_)/sizeof(*blockHeight_));
int depth = 2;
string _ = "POSSIBLE";
END
CASE(1)
int waterWidth = 3;
int landWidth = 3;
int blockHeight_[] = {3,4,4,5,6, 6};
vector <int> blockHeight(blockHeight_, blockHeight_+sizeof(blockHeight_)/sizeof(*blockHeight_));
int depth = 2;
string _ = "IMPOSSIBLE";
END
CASE(2)
int waterWidth = 5;
int landWidth = 2;
int blockHeight_[] = {4,4,4,4,4};
vector <int> blockHeight(blockHeight_, blockHeight_+sizeof(blockHeight_)/sizeof(*blockHeight_));
int depth = 4;
string _ = "POSSIBLE";
END
CASE(3)
int waterWidth = 5;
int landWidth = 5;
int blockHeight_[] = {5,5,5,5,5,5, 2,3,4,4,6, 7, 3, 2};
vector <int> blockHeight(blockHeight_, blockHeight_+sizeof(blockHeight_)/sizeof(*blockHeight_));
int depth = 2;
string _ = "POSSIBLE";
END
CASE(4)
int waterWidth = 5;
int landWidth = 7;
int blockHeight_[] = {6,6,6,6,6,6,6, 6,6,6,6,6,7,8,9,10};
vector <int> blockHeight(blockHeight_, blockHeight_+sizeof(blockHeight_)/sizeof(*blockHeight_));
int depth = 5;
string _ = "POSSIBLE";
END
CASE(5)
int waterWidth = 1;
int landWidth = 1;
int blockHeight_[] = {5,3,4};
vector <int> blockHeight(blockHeight_, blockHeight_+sizeof(blockHeight_)/sizeof(*blockHeight_));
int depth = 2;
string _ = "IMPOSSIBLE";
END
CASE(6)
int waterWidth = 3;
int landWidth = 1;
int blockHeight_[] = {2, 3, 4, 5};
vector <int> blockHeight(blockHeight_, blockHeight_+sizeof(blockHeight_)/sizeof(*blockHeight_));
int depth = 2;
string _ = "IMPOSSIBLE";
END
/*
CASE(7)
int waterWidth = ;
int landWidth = ;
int blockHeight_[] = ;
vector <int> blockHeight(blockHeight_, blockHeight_+sizeof(blockHeight_)/sizeof(*blockHeight_));
int depth = ;
string _ = ;
END
*/
}
// END CUT HERE