1 int main()
 2 {
 3     vector<string> str;
 4     string str1;
 5     while (cin >> str1)
 6     {
 7         auto last = str.end();
 8         if (str.size() != 0 && str1 == (*(last-1)))
 9         {
10             cout << str1 << endl;
11             break;
12         }
13         else
14             str.push_back(str1);
15     }
16     system("pause");
17     return 0;
18 }