Ridhiman challenged Ashish to find the maximum valued subsequence of an array a of size n consisting of positive integers.

The value of a non-empty subsequence of k elements of a is defined as ∑2i over all integers i≥0 such that at least max(1,k?2) elements of the subsequence have the i-th bit set in their binary representation (value x has the i-th bit set in its binary representation if ?x2i?mod2 is equal to 1).

Recall that b is a subsequence of a, if b can be obtained by deleting some(possibly zero) elements from a.

Help Ashish find the maximum value he can get by choosing some subsequence of a.

Input
The first line of the input consists of a single integer n (1≤n≤500) — the size of a.

The next line consists of n space-separated integers — the elements of the array (1≤ai≤1018).

Output
Print a single integer — the maximum value Ashish can get by choosing some subsequence of a.

Examples
Input
3
2 1 3
Output
3
Input
3
3 1 4
Output
7
Input
1
1
Output
1
Input
4
7 7 1 1
Output
7
Note
For the first test case, Ashish can pick the subsequence {2,3} of size 2. The binary representation of 2 is 10 and that of 3 is 11. Since max(k?2,1) is equal to 1, the value of the subsequence is 20+21 (both 2 and 3 have 1-st bit set in their binary representation and 3 has 0-th bit set in its binary representation). Note that he could also pick the subsequence {3} or {2,1,3}.

For the second test case, Ashish can pick the subsequence {3,4} with value 7.

For the third test case, Ashish can pick the subsequence {1} with value 1.

For the fourth test case, Ashish can pick the subsequence {7,7} with value 7.

思路：對于n<3的數組來說，我們可以直接暴力求出來。
對于n>=3的數組，我們選擇k==3的時候，一定是最優的。因為max(3-2,1)==1.如果原來選擇的3個數，第i位有1個1，但是呢，加進來的這個數字，第i個不為0，這樣的話，加進來的這個數，不僅沒有貢獻，還會拉低價值。比4更高的也是一樣。
代碼如下：

#include<bits/stdc++.h> #define ll long long using namespace std;const int maxx=5e2+10; ll a[maxx]; int num[maxx]; int n;int main() {scanf("%d",&n);for(int i=1;i<=n;i++) scanf("%lld",&a[i]);ll ans=0;for(int i=1;i<=n;i++){ans=max(ans,a[i]);for(int j=i+1;j<=n;j++){ans=max(ans,a[i]|a[j]);for(int k=j+1;k<=n;k++) ans=max(ans,a[i]|a[j]|a[k]);}}cout<<ans<<endl;return 0; }

努力加油a啊，(^o)/~

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