#include <iostream>
using namespace std;

int main(void)
{
    int n;
    unsigned int a[100000];
    int b[32] = {0};
    cin >> n;
    for(int i = 0; i < n; i++)
        cin >> a[i];
    for(int i = 0; i < n; i++)
        for(int j = 0; j < 32; j++)
            if((a[i] & (1 << j)) > 0)
                b[j]++;
    int m = 0;
    for(int i = 0; i < 32; i++)
        if(b[i] == n)
            m |= 1 << i;
    unsigned int res = 0;
    for(int i = 0; i < n; i++)
        res = max(res, a[i] ^ m);
    cout << res << endl;
    return 0;
}