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

import (
	"fmt"
	"sort"
)

func max(n, m int64) int64 {
	if n < m {
		return m
	} else {
		return n
	}
}

func main() {
	for {
		var N int
		var M int64
		fmt.Scan(&N, &M)
		if N == 0 && M == 0 {
			break
		}

		arr := make([]int64, N+1)
		for i := 1; i <= N; i++ {
			fmt.Scan(&arr[i])
		}
		sort.Slice(arr, func(i, j int) bool { return arr[i] < arr[j] })

		sums := make([]int64, len(arr)*len(arr))
		for i := 0; i < len(arr); i++ {
			for j := 0; j < len(arr); j++ {
				sums[i*len(arr)+j] = arr[i] + arr[j]
			}
		}

		sort.Slice(sums, func(i, j int) bool { return sums[i] < sums[j] })

		var m int64 = 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++: // Didn't see editorial
#include <iostream>
#include <queue>
#include <iomanip>
#include <map>
#include <algorithm>

using namespace std;

using ll = long long;
const ll INF = 1e9;
const ll MOD = 1e9 + 7;

int main() {
    while(true) {
        int N; ll M;
        cin >> N >> M;
        if (N == 0) return 0;
        vector<ll> P;
        for (int i = 0; i < N; i++) {
            ll p;
            cin >> p;
            P.push_back(p);
            P.push_back(p);
            P.push_back(p);
            P.push_back(p);
        }
        sort(P.begin(), P.end(), greater<>());
        N *= 4;

        ll dp[4002][5] = {};  // dp[i][k] := i???????????§??§k??¬???????????¨???????????§???
        for (int i = 0; i < N; i++) {
            for (int k = 0; k < 4; k++) {
                if (i < k) continue;

                dp[i+1][k] = max(dp[i+1][k], dp[i][k]);
                if (dp[i][k] + P[i] <= M) {
                    dp[i+1][k+1] = max(dp[i+1][k+1], dp[i][k] + P[i]);
                }
            }
        }

//        for (int i = 0; i < N; i++) {
//            for (int k = 0; k < 5; k++) {
//                cout << dp[i][k] << " ";
//            }
//            cout << "( " << P[i];
//            cout << endl;
//        }
//
//        for (int i = 0; i < 5; i++) {
//            cout << dp[N][i] << endl;
//        }
        cout << max(dp[N][0], max(dp[N][1], max(dp[N][2], max(dp[N][3], dp[N][4])))) << endl;
    }
}

C++: #include <cstdio>
#include <cctype>
#include <utility>
#include <vector>
#include <algorithm>
#include <array>
#include <numeric>
using namespace std;

const auto gcu = getchar_unlocked;
const auto pcu = putchar_unlocked;
#define _T template <typename T>
#define _HT template <typename H, typename... T>
#define _il inline
#define _sc _il bool scan
_T T in(int c){T n=0;int m=1;while(isspace(c)){c=gcu();}if(c=='-')m=-1,c=gcu();
	do{n=10*n+(c-'0'),c=gcu();}while(c>='0'&&c<='9');return m*n;}
_il int in() {return in<int>(gcu());}
_T T scan(T &n){int c=gcu();return c==EOF?false:(n=in<T>(c),true);}
_sc(char &c){c=gcu();gcu();return c!=EOF;}
#ifdef _GLIBCXX_STRING
_sc(string &s){int c;s="";
	for(;;){c=gcu();if(c=='\n'||c==' ')return true;else if(c==EOF)return false;s+=c;}}
#endif
_HT _sc(H &h, T&&... t){return scan(h)&&scan(t...);}
#define _ot _il void out
#define _ol _il void outl
_ot(bool b) {pcu('0'+b);}
_ot(const char *s){while(*s)pcu(*s++);}
_ot(char c){pcu(c);}
#ifdef _GLIBCXX_STRING
_ot(string s){for(char c:s)pcu(c);}
#endif
_T _ot(T n){static char b[20];char *p=b,m=n<0?pcu('-'),-1:1;
	if(!n)*p++='0';else while(n)*p++=n%10*m+'0',n/=10;while(p!=b)pcu(*--p);}
_ol(){out('\n');}
#ifdef _GLIBCXX_VECTOR
_T _ot(vector<T> &v){for(T &x:v)out(&x == &v[0]?"":" "),out(x);outl();}
#endif
_HT _ot(H&& h, T&&... t){out(h);out(move(t)...);}
template <typename... T> _ol(T&&... t){out(move(t)...);outl();}

#define all(o) o.begin(), o.end()

void radix_sort(vector<int> &v) {
	vector<int> t(v.size());
	array<int, 256> c, s;
	for (int i = 0; i < 32; i += 8) {
		fill(all(c), 0);
		for_each(all(v), [&](int j) {c[(j >> i) & 255]++;});
		s.front() = 0;
		partial_sum(all(c) - 1, s.begin() + 1);
		for_each(all(v), [&](int j) {t[s[(j >> i) & 255]++] = j;});
		swap(v, t);
	}
}

int main() {
	for (int N, M; N = in(), M = in();) {
		vector<int> t(N), u;
		for (int &p: t)
			p = in();
		t.push_back(0);
		for (auto i = t.begin(); i != t.end(); i++)
			for (auto j = i; j != t.end(); j++)
				if (*i + *j <= M)
					u.push_back(*i + *j);
		radix_sort(u);
		int r = 0;
		for (auto i = u.begin(), e = u.end() - 1; i <= e; i++) {
			for (; *i + *e >= M; e--)
				;
			r = max(r, *i + *e);
		}
		outl(r);
	}
}

C++: #include <iostream>
using namespace std;
 
int main() {
	cin.tie(0);
   	ios::sync_with_stdio(false);
   	
	for(;;){
		/*入力*/
		int N,M;
		cin >> N >> M;
		if(N==0 && M==0)exit(0);
		int P[N+1],array[M+1]={0};
		P[0]=0;
		for(int i=1;i<=N;i++)cin >> P[i];
		for(int i=0;i<=N;i++)array[P[i]]=1;
 
 
		/*２投(０投１投を含む)で1からMまでが可能か判定*/
		for(int i=0;i<=N;i++){
			for(int j=0;j<=N;j++){
				if(P[i]+P[j] <= M)array[P[i]+P[j]]=1;
			}
		}
 
		/*４投に拡張*/
		int p[M+1]={0};
		for(int i=1;i<=M;i++){
				if(array[i]==1)p[i]=i;
		}
		for(int i=0;i<=M;i++){
			for(int j=0;j<=M;j++){
				if(p[i]+p[j] <= M)array[(p[i]+p[j])]=1;
			}
		}
 
		/*判定出力*/
		for(int i=M;i>0;i--){
			if(array[i]==1){
				cout << i << endl;
				break;
			}
		}
	}
	return 0;
}

C++: 
#include<stdio.h>
#include<stdlib.h>
#include<math.h>

int main()
{
	int ans[4];
	int temp;
	double energy,energy_min,energy_now;
	int M, N;
	int* p;
	int i, j;
	double T=100;
	int ret;
	while (1) {
		scanf("%d%d", &N, &M);
		p = (int*)malloc((N+1) * sizeof(int));
		for (i = 0; i < N; i++) {
			scanf("%d", &p[i]);
		}
		p[N] = 0;
		if (N == M && N == 0) {
			break;
		}
		energy_min = pow(10, 300);
		for (j = 0; j < 4; j++) {
			ans[j] = p[(int)((double)(rand() + 1) / (RAND_MAX + 2)*(N+1))];
		}
		
		for (T = 100000; T > 100; T--) {
			for (j = 0; j < 4; j++) {
				temp = p[(int)((double)(rand() + 1) / (RAND_MAX + 2)*(N+1))];
				for (j = 0; j < 4; j++) {
					ret = ans[0] + ans[1] + ans[2] + ans[3];
					ret += temp - ans[j];
					energy = M - ret;
					if (M < ret)energy += 100000000;

					if (energy < energy_min) {
						energy_min = energy;
						ans[j] = temp;
					}
					else if ((double)(rand() + 1) / (RAND_MAX + 2) < exp((energy_min - energy) / T*1000)) {
						energy_min = energy;
						ans[j] = temp;
					}
				}

			}
		}
		ret=ans[0]+ +ans[1] + ans[2] + ans[3];
		printf("%d\n", ret);
	}
    return 0;
}

C++: #include <iostream>
#include <vector>
#include <queue>
#include <stack>
#include <map>
#include <set>
#include <algorithm>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#define REP(i, n) for(int i = 0;i < n;i++)
#define REPR(i, n) for(int i = n;i >= 0;i--)
#define FOR(i, m, n) for(int i = m;i < n;i++)
#define FORR(i, m, n) for(int i = m;i >= n;i--)
#define SORT(v, n) sort(v, v+n);
#define VSORT(v) sort(v.begin(), v.end());
#define llong long long
#define pb(a) push_back(a)
#define INF 999999999
using namespace std;
typedef pair<int, int> P;
typedef pair<llong, llong> LP;
typedef pair<int, P> PP;
typedef pair<llong, LP> LPP;

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

int main(){
	while(1){
		llong n, m;
		scanf("%lld%lld", &n, &m);
		if(n==0) return 0;

		vector<llong> v(n);
		REP(i, n){
			scanf("%lld", &v[i]);
		}
		v.push_back(0);
		n++;

		vector<llong> a;
		REP(i, n){
			REP(j, n){
				a.push_back(v[i]+v[j]);
			}
		}
		VSORT(a);

		llong ans=0;
		REP(i, n){
			REP(j, n){
				llong tmp=v[i]+v[j];
				llong k=upper_bound(a.begin(), a.end(), m-tmp)-a.begin();
				if(k==a.size()) continue;
				k--;

				if(k>=0) ans=max(ans, tmp+a[k]);
			}
		}

		printf("%lld\n", ans);
	}
}