小A的位运算

异或大值即可

#include<bits/stdc++.h>
using namespace std;
#define ll long long
int const N=5e6+7;
ll a[N];
int n;
bool cmp(ll a,ll b){
    return a>b;
}
ll ans,cnt;
int main(){
    cin >> n;
    for(int i=1;i<=n;++i){
        cin >> a[i];
    }
    sort(a+1,a+n+1,cmp);
    for(int i=1;i<=n;++i){
        if( (ans|a[i])>ans && cnt+1<=n-1 ){
            ans=ans|a[i];
            cnt++;
        }
    }
    cout << ans ;
    return 0;
}