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+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 <bits/stdc++.h>
using namespace std;

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  int N, M;
  while (true) {
    cin >> N >> M;
    if (N == 0 && M == 0) break;
    int P[N + 1];
    P[0] = 0;
    int ans = 0;
    for (int i = 0; i < N; i++) {
      cin >> P[i + 1];
    }
    vector<int> v;
    for (int i = 0; i <= N; i++) {
      for (int j = 0; j <= N; j++) {
        if (P[i] + P[j] <= M) v.push_back(P[i] + P[j]); 
      }
    }
    sort(v.begin(), v.end());
    for (int i = 0; i < v.size(); i++) {
      int res = M - v[i];
      if (res == 0) {
        ans = M;
        break;
      }
      int left = -1;
      int right = v.size();
      while (right - left > 1) {
        int mid = (right + left) / 2;
        if (res >= v[mid]) left = mid;
        else right = mid;
      }
      ans = max(ans, v[i] + v[left]);
    }
    cout << ans << "\n";
  }
  return 0;
}

C++: #include <cstdio>
#include <cstring>
#include <vector>
#include <algorithm>

using namespace std;

const int INF = 1<<30;

int N,M;

int main(){
  while(scanf("%d%d", &N,&M) && N||M){
    vector<int>a,v;
    a.push_back(0);
    for(int i=0;i<N;i++){
      int x;scanf("%d", &x);
      a.push_back(x);
    }
    for(int i=0;i<=N;i++) for(int j=0;j<=N;j++){
	if(a[i]+a[j] <= M) v.push_back(a[i]+a[j]);
    }
    v.push_back(INF);

    sort(v.begin(), v.end());
    int res = 0;
    for(int i=0;i<v.size()-1;i++){
      int x = M-v[i];
      vector<int>::iterator it = upper_bound(v.begin(), v.end(), x); if(it != v.begin()) it--;
      res = max(res, v[i] + *it);
    }
    printf("%d\n", res);
  }
  return 0;
}

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

using namespace std;

int main ( void )
{
	int n, m;
	int p[1000];
	set<int> S;
	
	while ( cin >> n >> m, (n | m) )
	{
		int ans = 0;
		S.clear();
		S.insert(0);
		for ( int i = 0; i < n; ++i )
		{
			cin >> p[i];
			if ( p[i] < m )
			{
				S.insert(p[i]);
				ans = max( ans, p[i] );
			}
		}
		
		for ( int i = 0; i < n; ++i )
		{
			for ( int j = i; j < n; ++j )
			{
				int x = p[i] + p[j];
				if ( x <= m )
				{
					S.insert(x);
					ans = max( ans, p[i] );
				}
			}
		}
		
		if ( S.count(m) )
		{
			cout << m << endl;
			continue;
		}
		
		for ( int i = 0; i < n; ++i )
		{
			for ( int j = i; j < n; ++j )
			{
				int x = p[i] + p[j];
				if ( x <= m )
				{
					int y = m - x;
					while ( !S.count(y) && ( ans < (x + y) ) )
					{
						--y;
					}
					ans = max( ans, (x + y) );
				}
			}
		}
		
		cout << ans << endl;
	}
	
	return 0;
}

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 _DEF(r, n, ...) inline r n(__VA_ARGS__) noexcept
#define _T template <typename T>
#define _HT template <typename H,typename... T>
_T _DEF(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;}
_DEF(int, in){return in<int>(gcu());}
#define _SCAN(...) _DEF(bool,scan,__VA_ARGS__)
_T _SCAN(T &n){int c=gcu();return c==EOF?false:(n=in<T>(c),true);}
_DEF(bool, scan, char &c){c=gcu();gcu();return c!=EOF;}
#ifdef _GLIBCXX_STRING
_SCAN(string &s){int c;s="";
	for(;;){c=gcu();if(c=='\n'||c==' ')return true;else if(c==EOF)return false;s+=c;}}
#endif
_HT _SCAN(H &h,T&&... t){return scan(h)&&scan(t...);}
#define _OUT(...) _DEF(void,out,__VA_ARGS__)
#define _OUTL(...) _DEF(void,outl,__VA_ARGS__)
_OUT(bool b){pcu('0'+b);}
_OUT(const char *s){while(*s)pcu(*s++);}
_OUT(char c){pcu(c);}
#ifdef _GLIBCXX_STRING
_OUT(string s){for(char c:s)pcu(c);}
#endif
_T _OUT(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);}
_OUTL(){out('\n');}
#ifdef _GLIBCXX_VECTOR
_T _OUT(vector<T> &v){for(T &x:v)out(&x == &v[0]?"":" "),out(x);outl();}
#endif
_HT _OUT(H&& h, T&&... t){out(h);out(move(t)...);}
template <typename... T> _OUTL(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 <cstdio>
#include <cctype>
#include <utility>
#include <vector>
#include <algorithm>
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();}

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);
		sort(t.begin(), t.end());
		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);
		sort(u.begin(), u.end());
//		u.erase(unique(u.begin(), u.end()), u.end());
		int r = 0;
		for (auto i = u.begin(), e = u.end() - 1; i <= e; i++) {
			for (; *i + *e >= M; e--)
				;
			if (*i + *e > r)
				r = *i + *e;
		}
		outl(r);
	}
}