Compilare: user.cpp: In function ‘int main()’: user.cpp:19:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<s.length();i++){ ^ user.cpp:10:32: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("fences.in","r",stdin); ^ user.cpp:11:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("fences.out","w",stdout); ^