Compilare: user.cpp: In function ‘int main()’: user.cpp:30:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j=0;j<s.size();++j) ^ user.cpp:43:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j=0;j<s.size();++j) ^ user.cpp:61:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j=0;j<t[i].size();++j) ^ user.cpp:15:30: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("stive.in","r",stdin); ^ user.cpp:16:32: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("stive.out","w",stdout); ^ user.cpp:18:15: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&N); ^