Compilare: main.cpp: In function 'int main()': main.cpp:13:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < s.size(); ++i) { ~~^~~~~~~~~~ main.cpp:23:16: warning: array subscript has type 'char' [-Wchar-subscripts] fv[s[i]] = (fv[s[i]] + i + 1) % MOD; ^ main.cpp:23:28: warning: array subscript has type 'char' [-Wchar-subscripts] fv[s[i]] = (fv[s[i]] + i + 1) % MOD; ^