#include <bits/stdc++.h>
    using namespace std;
    #include <math.h>
    #include <iomanip>
    #include <cstdint>
    #include <string>
    #include <sstream>
    template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
    template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
    #define rep(i,n) for (int i = 0; i < (n); ++i)
    typedef long long ll;
    typedef long double ld;
    const int INF=1001001001;
    const int mod=998244353;
    
    void solve(){
        int n;
        cin>>n;
        vector<ll>a(n);
        rep(i,n) cin>>a[i];
        ll mx=*max_element(a.begin(),a.end());
        ll x=log2(mx)+1;
        ll y=(1ll<<x)-1;
        mx^=y;
        rep(i,n){
            for(ll j=0;j<60;j++){
                if(a[i]>>j&1){mx&=~(1ll<<j);}
            }
        }
        if(mx==0){mx=y+1;}
        cout<<mx<<endl;
    }

    int main(){
        ios_base::sync_with_stdio(false);
        cin.tie(NULL);
        
		solve();
        
        return 0;
    }