Compilare: user.cpp: In function ‘int find_hash(long long int)’: user.cpp:16:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<v[b].size();i++) ^ user.cpp: In function ‘int main()’: user.cpp:23:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("abc2.in","r",stdin); ^ user.cpp:24:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("abc2.out","w",stdout); ^ user.cpp:27:14: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(sir); ^ /tmp/ccmwo5U8.o: In function `main': user.cpp:(.text.startup+0x66): warning: the `gets' function is dangerous and should not be used.