#include <stdio.h>

int main() {
    int N;
    scanf("%d", &N);  
    
    int A;
    int result = 0; 
    
    
    for (int i = 0; i < N; i++) {
        scanf("%d", &A);
        result ^= A;  
    }
    
    
    printf("%d\n", result);
    
    return 0;
}