#include<bits/stdc++.h>
using namespace std;

int N;
int A[1000005];

/*
int dfs(int bit, int l, int r){
	if(bit < 0){
		for(int i = l; i < r; i++){

		}
	}

	int ll = l;
	int rr = r - 1;
	while(1){
		while(ll < N && (A[ll] & (1 << bit)) == 0) ll++;
		while(rr >= 0 && (A[rr] & (1 << bit)) != 1) rr--;
		if(ll >= rr) break;
		swap(A[ll], A[rr]);
		ll++;
		rr--;
	}

	return min(dfs(bit - 1, l, ll), dfs(bit - 1, rr + 1, r); 
}
*/
int cnt[100][2];
int main(){
	cin >> N;
	for(int i = 0; i < N; i++){
		cin >> A[i];
	}
	int ans = 0;
	for(int i = 0; i < 32; i++){
		cnt[i][0] = 0;
		cnt[i][1] = 0;
		for(int j = 0; j < N; j++){
			if((A[j] & (1 << i))){
				cnt[i][0]++;
			}else{
				cnt[i][1]++;
			}
		}
		if(cnt[i][0] != 0 && cnt[i][1] != 0){
			ans |= 1 << i;
		}
	}
	cout << ans << endl;
}