Go: ///
// File:  0529.go
// Author: ymiyamoto
//
// Created on Wed Feb 28 20:39:28 2018
//
package main

import (
	"fmt"
	"sort"
)

func max(n, m int) int {
	if n < m {
		return m
	} else {
		return n
	}
}

func main() {
	for {
		var N, M int
		fmt.Scan(&N, &M)
		if N == 0 && M == 0 {
			break
		}

		arr := make([]int, N+1)
		for i := 1; i <= N; i++ {
			fmt.Scan(&arr[i])
		}
		sort.Ints(arr)

		sums := make([]int, len(arr)*len(arr))
		for i := 0; i < len(arr); i++ {
			for j := 0; j < len(arr); j++ {
				sums[i+j] = arr[i] + arr[j]
			}
		}
		sort.Ints(sums)

		m := 0
		for i := 0; i < len(sums); i++ {
			rem := M - sums[i]
			if rem >= 0 {
				index := sort.Search(len(sums), func(i int) bool { return sums[i] > rem }) - 1
				if index >= 0 {
					m = max(m, sums[i]+sums[index])
				}
			}
		}
		fmt.Println(m)
	}
}

C++: #include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <climits>
#include <cmath>
#include <complex>
#include <map>
#include <set>
#include <vector>
#include <stack>
#include <queue>
#include <bitset>
#include <algorithm>
#include <numeric>
#include <functional>
#include <cassert>
#include <iomanip>
using namespace std;

#define Rep(b, e, i) for(int i = b; i <= e; i++)
#define Repr(e, b, i) for(int i = e; i >= b; i--)
#define rep(n, i) Rep(0, n-1, i)
#define repr(n, i) Repr(n-1, 0, i)
#define all(v) (v).begin(), (v).end()
#define pb(v) push_back(v)
#define uniq(v) (v).erase(unique(all(v)),(v).end())
#define bitcnt(x) __builtin_popcount(x)
#define fst first
#define snd second
#define Pqaz(T) priority_queue<T,vector<T>,greater<T>>
#define Pqza(T) priority_queue<T>
#define put(x) cout << x;
#define putsp(x) cout << x << ' ';
#define putbd cout << "---------------------------------------------" << endl;
#define putln(x) cout << x << endl;
#define debug(x) cerr << #x << "=" << x << endl;
#define ENJYU std::ios::sync_with_stdio(false);std::cin.tie(0);

typedef long long ll;
typedef pair<ll, ll> llP;
typedef pair<int, int> intP;
typedef complex<double> comp;
typedef vector <int> vec;
typedef vector <ll> vecll;
typedef vector <double> vecd;
typedef vector <vec> mat;
typedef vector <vecll> matll;
typedef vector <vecd> matd;

//vector の中身を出力
template <class T>ostream &operator<<(ostream &o,const vector<T>&v)
{o<<"{";for(int i=0;i<(int)v.size();i++)o<<(i>0?", ":"")<<v[i];o<<"}";return o;}

const int MAX = 200020;
const double PI = 3.14159265358979323846;
const double EPS = 1e-12;
const int INF = 1<<29;
const ll INFL = 1e18;
const int MOD = 1000000007;

const int dx[]={1,0,-1,0},dy[]={0,1,0,-1};
//const int dx[]={-1,-1,-1,0,1,1,1,0},dy[]={-1,0,1,1,1,0,-1,-1};

//********************************template END****************************************//

void solve(void){

	int N, M;
	cin >> N >> M;
	vec ns(N);
	rep(N, i)
	{
		cin >> ns[i];
	}
	vec ss;
	ss.pb(0);
	rep(N, i)
	{
		ss.pb(ns[i]);
		Rep(i, N-1, j)
		{
			ss.pb(ns[i]+ns[j]);
		}
	}
	sort(all(ss));
	uniq(ss);
	//cout << ss << endl;

	int ans = 0;

	rep(N, i) Rep(i, N-1, j)
	{
		int tmp = ns[i]+ns[j];
		int partner = *(upper_bound(all(ss), M-tmp)-1);
		if (tmp + partner <= M)
		{
			ans = max(ans, tmp + partner);
		}
	}

	cout << ans << endl;
}

int main(void){
	solve();
	//cout << "yui(*-v・)yui" << endl;
	return 0;
}

C++: #include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main(){

	int n,m;
	while(cin>>n>>m&&!(n==0&&m==0)){
		int scores[1001];
//		vector<int> comb;
		int comb[1000001];
		int cn=0;

		for(int i = 0; i < n; i++){
			cin>>scores[i];
		}
		scores[n]=0;
		for(int i = 0; i < n+1; i++){
			for(int j = 0; j < n+1; j++){
				int sum=scores[i]+scores[j];
				if(sum<=m){
					//comb.push_back(sum);
					comb[cn]=sum;
					cn++;
				}
			}
		}
		//sort(comb.begin(),comb.end());
		sort(comb,comb+cn);
		//comb.erase(unique(comb.begin(),comb.end()),comb.end());

		int maxNum=0;
		for(int i = 0; i < n; i++){
			for(int j = 0; j < n; j++){
				int left = (scores[i]+scores[j]);
				if(left<=m&&comb[0]+left<=m){
					//vector<int>::iterator it = lower_bound(comb.begin(),comb.end(),m-left);
					int *it = lower_bound(comb,comb+cn,m-left);
					if(it==comb+cn){
						maxNum=max(maxNum,comb[cn-1]+left);
					}
					else{
						if(*it==(m-left)){
							maxNum=m;
						}
						else{
							it--;
							maxNum=max(maxNum,*it+left);
						}
					}
				}
			}
		}
		cout<<maxNum<<endl;
	}

	return 0;
}