//sol 5369666174
#include<bits/stdc++.h>
using namespace std;

#define mxx 200005
#define ll long long
#define answ ((out)?"YES":"NO")
#define endl '\n'


void solve(int tc){
    int n;
    cin>>n;
    int out=0,a;
    for(int i=0;i<n;i++){
        cin>>a;
        out^=a;
    }
    cout<<out<<endl;
}


void sub_run(){
    #ifndef ONLINE_JUDGE
    freopen("inp.txt", "r", stdin);
    freopen("out.txt", "w", stdout);
    #endif // ONLINE_JUDGE
}
 
int main(){
    //ios_base::sync_with_stdio(false);
    //cin.tie(NULL);
 
    int t=1;
    // sub_run();
    // cin>>t;
    for(int i=1;i<=t;i++)solve(i);
}