#include<bits/stdc++.h>
#define lld long long 
#define gtc getchar()
using namespace std;
inline int read(){
	int an=0,t=1;
	char c=gtc;
	while(!isdigit(c))if(c=='-')t=-1,c=gtc;
	while(isdigit(c))an=an*10+(c-'0'),c=gtc;
	an*=t;
	return an;	
}
int m,n,ans;
int main()
{
	ios::sync_with_stdio(0);
	m=read();
	while(m--)
	{
		n=read();
		ans^=n;
	}
	cout<<ans;
	return 0;
}