#include<bits/stdc++.h>
#define ll long long
#define el '\n'
#define pb push_back
#define pb1 pop_back
#define swift ios_base::sync_with_stdio(0); cin.tie(nullptr);
#define pr cin.exceptions(ios::badbit | ios::failbit);
using namespace std;


int main() {

    swift;
    pr;

    ll tt=1;
    //cin>>tt;
    while(tt--) {
    ll n;
    cin>>n;
    vector<ll> v(n);
    for(auto &u:v) cin>>u;

    unordered_map<ll,ll> freq;

    for(ll i=0;i<n;i++) {
        freq[v[i]]++;
     }
     ll ans=0;
    for(ll i=0;i<n;i++) {
        if (freq[v[i]] == 1) ans=v[i];
    }
    cout<<ans<<el;
    }
    return 0;
}