Compilare: user.cpp: In function ‘bool found(ll)’: user.cpp:21:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0;i < h[y].size();i++) ^ user.cpp: In function ‘int main()’: user.cpp:30:33: 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:31:35: 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:33:13: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(s); ^ /tmp/ccMFPjS8.o: In function `main': user.cpp:(.text.startup+0x56): warning: the `gets' function is dangerous and should not be used.