Compilare: user.cpp: In function ‘int main()’: user.cpp:78:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i=0;i<u.size();++i) ^ user.cpp:55:30: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("senat.in","r",stdin); ^ user.cpp:56:32: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("senat.out","w",stdout); ^ user.cpp:58:31: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] for (scanf("%d%d\n",&N,&M),j=1;j<=M;++j) ^ user.cpp:60:12: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(w); ^ /tmp/ccD1I8Po.o: In function `main': user.cpp:(.text.startup+0x88): warning: the `gets' function is dangerous and should not be used.