#include <string.h>
#include<stdio.h> 
int main()
{
    int n = 0;
    
    scanf("%d",&n);
    int resault = 0;
    for(int i = 0; i < n; i++)
    {
        int temp = 0;
        scanf("%d",&temp);
        resault  ^= temp;
    }
    printf("%d",  resault);
    return 0;
}