#include<bits/stdc++.h>
using namespace std;
int main(){
    int N; cin>>N;
    int maher = 0;
    vector<int>A(N);
    for(int i = 0; i<N; i++){
        cin>>A[i];
         maher = maher^A[i];
    }
    
    cout<<maher<<endl;
}