Compilare: main.cpp: In function 'int main()': main.cpp:48:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=0;j<b.size();j++) ~^~~~~~~~~ main.cpp:40:37: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("artifact.in","r",stdin); ^ main.cpp:41:39: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("artifact.out","w",stdout); ^