#include <stdio.h>

int main() {
    int n = 0;
    scanf("%d", &n);
    int a[n];
    int ret = 0;

    for (int i = 0; i < n; i++)
    {
        scanf("%d", &a[i]);
        ret ^= a[i];
    }
    printf("%d", ret);

    return 0;
}