#include <bits/stdc++.h>
using namespace std;
#define int long long
#define INT_MAX (int)(1e18)

int n;

inline int read(){
    int x=0,f=1;char ch=getchar();
    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
    while(ch>='0'&&ch<='9')x=(x<<3)+(x<<1)+(ch^48),ch=getchar();
    return x*f;
}

void solve(){
    
}

signed main(){
    freopen("XORcipher.in","r",stdin);
    freopen("XORcipher.out","w",stdout);
    n=read();
    int ans=0;
    for(int i=1;i<=2*n;i++) ans^=read();
    cout<<ans<<"\n";
    return 0;
}