Compilare: user.cpp: In function ‘int main()’: user.cpp:41:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i=0;i<w.size();++i) ^ user.cpp:50:56: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (printf("%d %d\n",total,sol.size()),i=0;i<sol.size();++i) ^ user.cpp:28:28: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("apm.in","r",stdin); ^ user.cpp:29:30: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("apm.out","w",stdout); ^ user.cpp:31:25: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] for (scanf("%d%d",&N,&M);M;--M) ^ user.cpp:33:32: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d%d",&X,&Y,&cost); ^