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 <fstream>
#include <vector>
#include <string>
#include <map>
#include <sstream>
#include <queue>
#include <cstdlib>
#include <algorithm>
#include <iterator>
#include <stack>
#include <list>
using namespace std;
#define INF 100000000
typedef long long int lli;
typedef pair<int,int> P;

int p[1001];
int h[1000*1000+1];

int main(){
	int n,m,ans;
	while(cin>>n>>m){
		if(n==0&&m==0) break;
		p[0]=0;
		ans=0;
		for(int i=1; i<=n; ++i){
			cin >> p[i];
		}
		for(int i=0; i<=n; ++i){	
			for(int j=0; j<=n; ++j){
				h[i*n+j]=p[i]+p[j];
			}
		}
		sort(h,h+n*n+1);
		/*
		for(int i=0; i<=n*n; ++i){
			cout << h[i] << "\n";
		}
		*/
		for(int i=0; i<=n; ++i){	
			for(int j=0; j<=n; ++j){	
				int tmp=p[i]+p[j];
				int l=0,r=n*n;
				int cnt=0;
				while(1){
					int mid=(r+l)/2;
					if(cnt>=100){
						if(h[mid]+tmp<=m) ans=max(ans,h[mid]+tmp);
						break;
					}
					if(h[mid]+tmp>m){
						r=mid;
					} else if(h[mid]+tmp<m){
						l=mid;
					} else if(h[mid]+tmp==m){
						ans=m;
						break;
					}
					++cnt;
				}
			}
		}
		cout << ans << "\n";
	}
	return 0;
}

C++: #include<iostream>
#include<algorithm>
#include<iterator>
template<typename InIt>int*copy_n(InIt i,int n,int*o){for(*o++=*i;--n;)*o++=*++i;return o;}//ツ妥」ツ妥鳴品
using namespace std;
const int N=1000;
int*pe,p[1+N],*qe,q[1+N*N],n,m,v;
int main(){
	for(;cin>>n>>m,n;){
		v=*p=0;
		pe=copy_n(istream_iterator<int>(cin),n,p+1);
		sort(p,pe);
		pe=unique(p,pe);
		qe=q;
		for(int*i=p;i!=pe;++i)
			qe=transform(p,i+1,qe,bind2nd(plus<int>(),*i));
		sort(q,qe);
		qe=unique(q,qe);
		*qe++=m+1;//ツ氾板閉コ
		for(int*i=q;*i<=m;++i)
			v=max(v,*i+upper_bound(q+1,qe,m-*i)[-1]);
		cout<<v<<endl;
	}
	cout<<endl;
}

C++: #include <map>
#include <set>
#include <cmath>
#include <queue>
#include <stack>
#include <cctype>
#include <cstdio>
#include <string>
#include <vector>
#include <cstdlib>
#include <cstring>
#include <sstream>
#include <iostream>
#include <algorithm>
#include <functional>

#define INF (2 << 28)
#define fr first
#define sc second
using namespace std;

typedef long long ll;
typedef pair<int, int> iP;

int main(){
  
  int n, m, p[1111];
  int sum[1111111];

  while(cin >> n >> m, n||m){
    int idx = 0, maxi = 0;
    for(int i = 0; i < n; i++) cin >> p[i]; 
    p[n] = 0;
    
    for(int i = 0; i < n + 1; i++)
      for(int j = 0; j < n + 1; j++)
        sum[idx++] = p[i] + p[j];
    
    sort(sum, sum + idx);
    int l = 0, r = idx;
    while(l < r){
      bool judge = 0;
      int mid = (l + r + 1) / 2;
      for(int i = 0; i < idx; i++){
        if(sum[mid] + sum[i] <= m){
          maxi = max(maxi, sum[mid] + sum[i]);
          judge = 1;
        }
      } 
      if(judge) l = mid;
      else r = mid - 1;
    }
    cout << maxi << endl;
  }
}

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 <set>
#include <map>
#include <sstream>
#include <string>
#include <cstdio>
#include <stack>
#include <queue>
#include <algorithm>
#include <numeric>
#include <functional>
#include <cstring>
#include <tuple>
#include <utility>
#include <list>
#include <cmath>

using namespace std;

typedef long long LL;
typedef vector<int> Array;
typedef pair<int, int> P;

const LL LINF = 1LL << 60;
const LL MOD = 100000;
#define rep(i,n) for(int i=0;i<(int)n;++i)
#define all(c) (c).begin(), (c).end()

struct edge{ LL to, cost; edge(int t, LL c) :to(t), cost(c){} };

int dxk[] = { 1, 1, 1, 0, -1, 0 };
int dxg[] = { 0, 1, 0, -1, -1, -1 };
int dy[] = { -1, 0, 1, 1, 0, -1 };

int main()
{
	int n;
	LL m;
	vector<LL> anses;
	while (cin >> n >> m && n)
	{
		vector<LL> nums(n);
		rep(i, n) cin >> nums[i];
		vector<LL> arr(n*n + 2);
		rep(i, n) rep(j, n)
		{
			arr[i * n + j] = nums[i] + nums[j];
		}
		rep(i, n) arr[n*n + i] = nums[i];
		sort(all(arr));

		LL ans = 0;
		for (auto x : arr)
		{
			LL rem = m - x;
			auto it = upper_bound(all(arr), rem);
			if (it != arr.begin())
			{
				LL num = *(--it);
				ans = max(ans, num + x);
			}
		}
		cout << ans << endl;
		anses.push_back(ans);
	}
	cout << "anses" << endl;
	for (auto x : anses) cout << x << endl;
	cin >> n;
	return 0;
}