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 <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();}

void radix_sort(vector<int>::iterator b,vector<int>::iterator e) {
    vector<int> t(e - b);
    array<int, 256> c, s;
    for (int i = 0; i < 32; i += 8) {
        fill(c.begin(), c.end(), 0);
        for_each(b, e, [&](int j) {c[(j >> i) & 255]++;});
        s[0] = 0;
        partial_sum(c.begin(), c.end() - 1, s.begin() + 1);
        for_each(b, e, [&](int j) {t[s[(j >> i) & 255]++] = j;});
        copy(t.begin(), t.end(), b);
    }
}

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.begin(), u.end());
		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>
#include <vector>
#include <algorithm>
using namespace std;
#define MAX_N 1000

int n, m, ans;
int P[MAX_N+1];
vector<int> Q;

int BinarySearch(int q){
  int left = 0, right = Q.size();
  while(right - left > 1){
    int mid = (left + right) / 2;
    if(Q[mid] <= q) left = mid;
    else right = mid;
  }
  return left;
}

int main(void){
  while(cin >> n >> m && n != 0 && m != 0){
    P[0] = 0;
    for(int i = 1; i <= n; i++) cin >> P[i];
    Q.clear();
    for(int i = 0; i <= n; i++) for(int j = 0; j <= n; j++){
      int q = P[i] + P[j];
      Q.push_back(q);
    }
    sort(Q.begin(), Q.end());
    ans = 0;
    for(int i = 0; i < Q.size(); i++){
      if(Q[i] > m) break;
      int j = BinarySearch(m - Q[i]);
      int s = Q[i] + Q[j];
      if(s > ans) ans = s;
    }
    cout << ans << endl;
  }
  return 0;
}

C++: //include----------------------------------------------------------------------------------------------------------------------
#include <bits/stdc++.h>
//using namespace--------------------------------------------------------------------------------------------------------------
using namespace std;

//define-----------------------------------------------------------------------------------------------------------------------
#define rep(i, n) for(int i = 0; i < (int)n; i++)
#define FOR(i, s, n) for(int i = s; i < (int)n; i++)
#define per(i, n) for(int i = n; i >= 0; i--)
#define ROF(i, s, n) for(int i = s; i >= (int)n; i--)
#define FORIT(i, A) for (auto i : A)
#define PRINT(x) cout << (x) << "\n"
#define ALL(a) (a).begin(),(a).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define MP make_pair
#define EACH(i, n) for (__typeof((n).begin()) i = (n).begin(); i != (n).end(); ++i)
#define SZ(a) int((a).size())
#define EXIST(s,e) ((s).find(e)!=(s).end())
#define SORT(c) sort((c).begin(),(c).end())
#define CLR(a) memset((a), 0 ,sizeof(a))
#define dump(x) cout << #x << " = " << (x) << "\n";
#define debug(x) cout << #x << " = " << (x) << " (L" << __LINE__ << ")" << " " << __FILE__ << "\n";
#define sq(n) (n) * (n)

//typedef----------------------------------------------------------------------------------------------------------------------
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef long long LL;
typedef vector<LL> VLL;
typedef vector<VLL> VVLL;
typedef unsigned int uint;
typedef unsigned long long ull;
typedef priority_queue<int> maxpq;
typedef priority_queue< int, vector<int>, greater<int> > minpq;
//const------------------------------------------------------------------------------------------------------------------------
static const double EPS = 1e-10;
static const double PI = acos( -1.0 );
static const int mod = 1000000007;
static const int INF = 1 << 25;
static const LL LL_INF = 1152921504606846976;
//global-----------------------------------------------------------------------------------------------------------------------
LL n, m, ans = 0;
VI a;
//#define DEBUG
//function-------------------------------------------------------------------------------------------------------------------
int main() {
	while ( scanf( "%lld %lld", &n, &m ) && n && m ) {
		a.resize( n );
		rep( i, n ) {
			scanf( "%lld", &a[ i ] );
		}
		ans = 0;
		sort( a.rbegin(), a.rend() );
		rep( i, n ) {
			while ( ans <= m ) {
				ans += a[ i ];
			}
			ans -= a[ i ];
		}
		printf( "%lld\n", ans );
	}
	return 0;
}

C++: #include<iostream>
#include<algorithm>
#include<stdio.h>
#include<vector>
using namespace std;
int main()
{
	int n, m;
	int p;
	vector<int> g;
	cin >> n >> m;
	for (int i = 0; i < n; i++){
		cin >> p;
		g.push_back(p);
	}
	for (int i = 0; i < n; i++){
		for (int i2 = 0; i2 < n; i2++){
			g.push_back(g[i]+g[i2]);
		}
	}
	int x, y;
	x = 0; y = g.size() - 1;
	int maxv = 0;
	sort(g.begin(), g.end());
	while (1){
		if (g[x] + g[y] > maxv&&g[x] + g[y] <= m)maxv = g[x] + g[y];
		if (g[x] + g[y] <= m)x++;
		if (g[x] + g[y] > m)y--;
		if (x > y)break;
	}
	cout << maxv << endl;
}