Compilare: user.cpp: In function ‘int main()’: user.cpp:34:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<ret[n+1].size();i++) ^ user.cpp: In function ‘void initialize()’: user.cpp:63:31: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("pm.in","r",stdin); ^ user.cpp:64:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("pm.out","w",stdout); ^