Compilare: main.cpp: In function 'int main()': main.cpp:23:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < a.size(); i++) f[a[i] - 'a']++; ~~^~~~~~~~~~ main.cpp:29:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < b.size(); i++) mi = min(mi, f[b[i] - 'a']); ~~^~~~~~~~~~ main.cpp:35:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(k = 0; k < b.size(); k++) ~~^~~~~~~~~~ main.cpp:41:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(k == b.size()) { mi = med; st = med + 1; } ~~^~~~~~~~~~~