Compilare: user.cpp: In function ‘int main()’: user.cpp:35:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=1;i<s.size();i++) ^ user.cpp:36:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(i!=s.size()-1 && cond(s[i-1]-'a',s[i]-'a',s[i+1]-'a')) ^ user.cpp:51:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<s.size();i++) ^