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++: #include<algorithm>
#include<vector>
#include<cmath>

#define MAX_N 1001

using namespace std;

int BinSearch(int v[], int vsize, int search){
	int l = 0;
	int r = vsize;
	int m = 0;
	if( v[r - 1] < search ){
		return r - 1;
	}else if(v[1] > search ){
		return 0;
	}
	while( r - 1 > l ){
		m = (r + l) / 2;

		if( v[m] > search ){
			r = m;
		}else if(v[m] == search){
			return m;
		}else{
			l = m;
		}
	}
	return m;
}

void Merge(int a[], int p ,int q, int r){
	int i, j;
	int n1 = q - p;
	int n2 = r - q;
	int *L = new int[n1];
	int *R = new int[n2];

	for(i = 0; i < n1; i++)
		L[i] = a[p + i];

	for(j = 0; j < n2; j++)
		R[j] = a[q + j];

	i = 0;
	j = 0;

	for(int k = p; k < r; k++){
		if( i == n1 ){
			while( j < n2 ){
				a[k] = R[j];k++;j++;
			}
			break;
		}else if( j == n2 ){
			while( i < n1 ){
				a[k] = L[i];k++;i++;
			}
			break;
		}else{
			if( L[i] <= R[j] ){
				a[k] = L[i];
				i++;
			}else{
				a[k] = R[j];
				j++;
			}
		}
	}

	delete[] L;
	delete[] R;
}

void InsertionSort(int *a, int n){
	for(int i = 1; i < n; i++){
		int v = a[i], j;
		for(j = i; j > 0; j--)
			if( v < a[j - 1])
				a[j] = a[j - 1];
			else
				break;
		a[j] = v;
	}
}

void MergeSort(int a[], int p, int r){
	if( p < r ){
		if( r - p < 9 ){
			InsertionSort(a + p, r - p);
			return ;
		}
		int q = (p + r) / 2;
		MergeSort(a, p, q);
		MergeSort(a, q, r);
		Merge(a, p, q, r);
	}
}

int main(void){
	while( true ){
		int prevQ = -1;
		int index = 0;
		int Max = 0;
		int N, M;
		int *Q;
		int V[MAX_N];

		cin >> N >> M;
		
		if( N == 0 && M == 0 ){
			break;
		}

		for(int i = 0; i < N; i++){
			cin >> V[i];
		}
		V[N] = 0;
		N++;

		Q = new int[N*N];

		for(int i = 0; i < N; i++){
			for(int j = 0; j < N; j++){
				Q[i * N + j] = V[i] + V[j];
			}
		}
		//cout << "Sorting..." << endl;
		/*for(int i = 0; i < N * N; i++){
			cout << Q[i] << '\n';
		}*/
		
		MergeSort(Q, 0, N * N);
		//stable_sort(Q.begin(), Q.end());

		//cout << "Sorted:" << endl;
		/*for(int i = 0; i < N * N; i++){
			cout << Q[i] << '\n';
		}*/

		//cout << "Uniqing..." << endl;
		//Uniq( Q );

		for(int i = 0; i < N * N; i++){
			//cout << Q[i];
			if( prevQ == Q[i] ){
				continue;
			}else{
				prevQ = Q[i];
			}
			int optim = BinSearch(Q, N*N, M - Q[i]);
			//cout << ' ' << optim << ":" << Q[optim] << '\n';
			if( optim > 0 && Q[i] + Q[optim] > M) optim--;
			Max = max( Max , Q[i] + Q[optim] > M ? 0 : Q[i] + Q[optim]);
		}

		delete[] Q;
		cout << Max << '\n';
	}
	return 0;
}

C++: #include<iostream>
#include<string>
#include<vector>
#include<cstdio>
#include<map>
#include<algorithm>
#include<stack>
#define P pair<int,int>
using namespace std;

int g[1000005];
int main() {
	int a, b, c[1001];
	while (scanf("%d%d", &a, &b), a | b) {
		for (int d = 0; d < a; d++)scanf("%d", &c[d+1]);
		c[0] = 0;
		int sum = 0;
		for (int e = 0; e <= a; e++) {
			for (int f = e; f <= a; f++) {
				g[sum] = c[e] + c[f];
				sum++;
			}
		}
		sort(g, g + sum);
		int MAX = 0;
		for (int l = 0; l < sum; l++) {
			auto x = upper_bound(g, g + sum, b - g[l]);
			x--;
			printf("%d %d\n", g[l], *x);
		if(g[l]<=b)	MAX = max(MAX, g[l] + *x);
		}
		cout << MAX << endl;
	}
}

C++: #include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <cmath>
#include <cstdio>
#include <functional>
#include <numeric>
#include <stack>
#include <queue>
#include <map>
#include <set>
#include <utility>
#include <sstream>
#include <complex>

using namespace std;

#define FOR(i,a,b) for(long long i=(a);i<(b);i++)
#define REP(i,N) for(long long i=0;i<(N);i++)
#define ALL(s) (s).begin(),(s).end()
#define fi first
#define se second

#define PI acos(-1.0)
#define INF 1000000007
#define EPS 1e-10
#define MAX_N 20000
#define MAX_M 16

typedef long long ll;
typedef pair<ll, ll> P;
typedef pair<double, double> PD;
typedef pair<string, ll> PS;
typedef vector<ll> V;
typedef pair<P, char> PC;

int n, m, p[1010];
int dp[1010];

int main(){
	while (cin >> n >> m&&n + m){
		int i = 0;
		fill(dp, dp + 1010, 0);
		p[0] = 0;
		FOR(i, 1, n + 1)cin >> p[n];
		/*REP(i, 4){
			REP(j, n + 1){
			int now = dp[j];
			REP(k, n + 1){
			if (dp[j] + p[k] <= m){

			}
			}
			}
			}*/
		REP(i, m){
			i++;
		}
		cout << i << endl;
	}
}

C++: #include <vector>
#include <algorithm>
#include <set>
#include <map>
#include <queue>
#include <stack>
#include <iostream>
#include <cstdio>
#include <cmath>
#include <cstring>
using namespace std;
typedef long long ll;
typedef pair<ll,ll> P;
typedef double db;

#define fr first
#define sc second
#define pb push_back
#define rep(i,x) for(ll i=0;i<x;i++)
#define rep1(i,x) for(ll i=1;i<=x;i++)
#define rrep(i,x) for(ll i=x-1;i>=0;i--)
#define rrep1(i,x) for(ll i=x;i>0;i--)

ll n,m;
ll p[1001];
vector<ll> v;
int main()
{while(1){
	v.clear();
	cin>>n>>m;
	if(!n) break;
	p[0]=0;
	rep1(i,n) cin>>p[i];
	rep(i,n+1) rep(j,n+1){
		v.pb(p[i]+p[j]);
	}
	sort(v.begin(),v.end());
	ll ans;
	ans=0;
	//ans=v[upper_bound(v.begin(),v.end(),m)-v.begin()-1];
	rep(i,n+1) rep(j,n+1){
		if(p[i]+p[j]<=m) ans=max(ans,v[upper_bound(v.begin(),v.end(),m-p[i]-p[j])-v.begin()-1]+p[i]+p[j]);
	}
	//for(ll i=n/2;i<n;i++) if(p[i]<=m) ans=max(ans,v[upper_bound(v.begin(),v.end(),m-p[i])-v.begin()-1]+p[i]);
	//for(ll i=n/2;i<n;i++) for(ll j=i+1;j<n;j++) if(p[i]+p[j]<=m) ans=max(ans,v[upper_bound(v.begin(),v.end(),m-p[i]-p[j])-v.begin()-1]+p[i]+p[j]);
	//vector<ll>(v).swap(v);
	cout<<ans<<endl;
}}

C++: #include <iostream>
#include <string>
#include <sstream>
#include <vector>
#include <algorithm>
#include <numeric>
#include <set>
#include <map>
#include <queue>
#include <cstdio>
#include <cmath>
#include <ctime>
#include <cstring>
#include <cctype>
#include <cassert>
#include <cmath>
#include <limits>
#include <functional>

#define REP(i,n) for(int i=0;i<n;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 pb(x) push_back(x) 
#define SORT(x) sort((x).begin(),(x).end())
#define INF 999999999

using namespace std;

#define int long long

signed main(){
	int n, m;
	cin >> n >> m;
	vector<int> p(n);
	REP(i, n){
		cin >> p[i];
	}
	p.push_back(0);
	sort(p.begin(), p.end());
	n++;
	
	vector<int> v;
	REP(i, n){
		REP(j, n){
			v.push_back(p[i]+p[j]);
		}
	}
	SORT(v);
	
	int l=0, r=v.size()-1, ans=0;
	REP(i, 1000000){
		int k=v[l]+v[r];
		if(k>m){
			if(r>0) r--;
		}
		else if(k<=m){
			ans=max(ans, k);
			if(l<v.size()-1) l++;
		}
	}
	
	cout << ans << endl;
}