#include<iostream>

using namespace std;

int arr[500005];

int main()
{
    int n;
    cin >> n;

    long long int a;
    int p = 0;

    arr[0] = -1;
    for (int i = 0; i < n; i++)
    {

        cin >> a;

        if (a == arr[p] || p == 0)
        {
            p++;
            arr[p] = a;
        }
        else
            p--;
    }

    cout << arr[1] << endl;

}

Edited by author 12.12.2014 12:48

Edited by author 12.12.2014 12:48