Compilare: user.cpp: In function ‘void compute()’: user.cpp:15:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=0;j<v[i].size();++j) { ^ user.cpp: In function ‘int main()’: user.cpp:58:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("alpin.in","r",stdin); ^ user.cpp:59:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("alpin.out","w",stdout); ^ user.cpp:60:19: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&N); ^ user.cpp:63:27: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&x); ^