#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define F(i,a,b) for(ll i = a;i <= b;i++)
#define D(i,a,b) for(ll i = a;i >= b;i--)
#define fi first
#define se second
#define pii pair<int,int>
#define pb(x) push_back(x)
const int N = 1510,M = 2e6+10;
const ll inf = 1e17,mod = 998244353;

ll read(){
    ll x = 0,f = 1;char c = getchar();
    for(;c < '0' || c > '9';c = getchar())if(c == '-')f = -1;
    for(;c >= '0' && c <= '9';c = getchar())x = (x<<3) + (x<<1) + c-'0';
    return x * f;
}

int n;
ll x;
int main(){
    freopen("chopsticks.in","r",stdin);
    freopen("chopsticks.out","w",stdout);
    n = read();
    F(i,1,n)x ^= read();
    printf("%lld\n",x);

    return cerr<<endl<<"Time:"<<clock()<<"ms"<<endl,0;

}