#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
const ll mod=1e9+7;
ll rn[2000000];
mt19937 akil(chrono::steady_clock::now().time_since_epoch().count());
/*ll my_rand(int l, int r)
{
    return uniform_int_distribution<ll>(l, r) (akil);
}*/

void sufi() {
  int n;
  cin>>n;
  ll ara[n+1];
  map<ll,int>mp;
  for(int i=1;i<=n;i++){cin>>ara[i];mp[ara[i]]++;}
  for(int i=1;i<=n;i++){
    if(mp[ara[i]]==1){
        cout<<ara[i]<<endl;
        return;
    }
  }


}

int main() {
  //for(int i=0;i<2000000;i++)rn[i]=my_rand(1,1e17);
    int t = 1;
    //cin>>t;
    while (t--) {
        sufi();
    }
}