Compilare: main.cpp: In function 'int main()': main.cpp:32:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0;i<s.size();i++){ ~^~~~~~~~~ main.cpp:54:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=1,j=s.size()-1;i<s.size();i++,j--){ ~^~~~~~~~~ main.cpp:19:33: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("chei.in","r",stdin); ^ main.cpp:20:35: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("chei.out","w",stdout); ^