void yes(){ cout << "YES" << endl; exit(0); } void no(){cout << "NO" << endl; exit(0); } string str; { cin >> str; for(int i=0; i<(int)str.size()-2; ++i){ // そういえばstr.size()はunsignedでしたね! if (str[i] == '5' && str[i+1] == '7' && str[i+2] == '5') yes(); } no(); }