Compilare: user.cpp: In function ‘int main()’: user.cpp:112:50: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<max(a[0].size(),a[1].size());i++) ^ user.cpp:114:48: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(isalpha(a[0][i]) && i<a[0].size()) ^ user.cpp:116:48: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(isalpha(a[1][i]) && i<a[1].size()) ^