Compilare: main.cpp: In function 'int main()': main.cpp:15:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<s.size();++i) frs[s[i]-'a']++; ~^~~~~~~~~ main.cpp:16:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<t.size();++i) frt[t[i]-'a']++; ~^~~~~~~~~