2141：2333（zznuoj）

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <map>
 4 #include <string>
 5 #include<cstring>
 6 #include<algorithm>
 7 #include<vector>
 8 typedef long long ll;
 9 const int maxn = 1010000;
10 using namespace std;
11 int n, m,res;
12 int a[maxn];
13 int b[maxn];
14 int main()
15 {
16     int n, m;
17     while (cin >> n >> m,n!=0&&m!=0)
18     {
19         int k = 0;
20         for (int i = 0; i < n; i++)
21             scanf("%d", &a[i]);
22         for (int i = 0; i < n; i++)
23             for (int j = 0; j < n; j++)
24                 b[k++] = a[i] + a[j];
25         sort(b, b + k);
26         int Max = -1;
27         for (int i = 0; i < k; i++)
28         {
29             int temp = upper_bound(b, b + k, m - b[i]) - b;
30             if (temp - 1 < 0) continue;
31             Max = max(Max, b[i] + b[temp - 1]);
32         }
33         cout << Max << endl;
34     }
35     return 0;
36 }