#include <bits/stdc++.h>

typedef long long ll;
typedef unsigned long long ull;

#define FOR(i,a,b) for(int (i)=(a);i<(b);i++)
#define REP(i,n) FOR(i,0,n)
#define RANGE(vec) (vec).begin(),(vec).end()

using namespace std;


class XorMinMax {
public:
    void solve(void) {
            int n;
            cin>>n;
            vector<int> a(n);
            REP(i,n)
                cin>>a[i];

            int x = 0;

            REP(k,30)
            {
                int m = 0;
                REP(i,n)
                {
                    if ((1<<k) & a[i])
                        ++m;
                }
                if (0 < m && m < n)
                    x |= (1<<k);
            }
            cout<<x<<endl;
    }
};

#if 1
int main(int argc, char *argv[])
{
        ios::sync_with_stdio(false);
        auto obj = new XorMinMax();
        obj->solve();
        delete obj;
        return 0;
}
#endif