Compilare: main.cpp: In function 'int main()': main.cpp:58:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=0;j<x.length();++j) { ~^~~~~~~~~~~ main.cpp:64:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<min.length();++i) { ~^~~~~~~~~~~~~ main.cpp:65:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=i+1;j<=min.length();++j) { ~^~~~~~~~~~~~~~ main.cpp:38:31: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("sub.in", "r", stdin); ^ main.cpp:39:33: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("sub.out", "w", stdout); ^