Compilare: user.cpp: In function ‘int win(int)’: user.cpp:17:16: warning: comparison of constant ‘-1’ with boolean expression is always false [-Wbool-compare] if(M[y]==-1) ^ user.cpp: In function ‘int main()’: user.cpp:28:31: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("pp.in","r",stdin); ^ user.cpp:29:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("pp.out","w",stdout); ^ user.cpp:31:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&n,&k); ^