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<string>
#include<cmath>
#include<queue>
#include<map>
#include<set>
#include<list>
#include<iomanip>
#include<vector>
#include<functional>
#include<algorithm>
#include<cstdio>
using namespace std;
long long a[1001];
long long b[1000000];
int main() {
	int n, m;
	while (cin >> n >> m&&n != 0 && m != 0) {
		for (int i = 0; i < n; i++) {
			cin >> a[i];
		}
		a[n] = 0;
		int f = 0;
		for (int i = 0; i <= n; i++) {
			for (int j = i; j <= n; j++) {
				b[f] = a[i] + a[j];
				f++;
			}
		}
		long long sum = 0;
		sort(b, b + f);
		for (int i = 0; i <= f; i++) {
			int s = 0, e = f, t;
			long long g = m - b[i];
			while (e - s > 1) {
				t = (e + s) / 2;
				if (b[t] > g) e = t;
				if (b[t] <= g) s = t;
			}
			if (b[i] + b[s] <= m) sum = max(sum, b[i] + b[s]);
			if (b[i] + b[e] <= m) sum = max(sum, b[i] + b[e]);
		}
		cout << sum << endl;
	}
}

C++: #include "bits/stdc++.h"
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
#define rep(i,n) for(ll i=0;i<(ll)(n);i++)
#define all(a)  (a).begin(),(a).end()
#define pb push_back
#define vi vector<int>
#define INF 999999999


template<class T>
T rev_lower_bound(vector<ll> &vec,T num){
    ll left=0, right=vec.size()+1, mid=(left+right)/2LL;
    while(left+1<right){
        if(vec[mid]<=num) left = mid;
        else    right= mid;
        mid = (left+right)/2LL;
    }
    return mid;
}


int main(){
    
    int n,m;
    while(cin>>n>>m&&n&&m){
        vi p(n);
        rep(i,n)cin>>p[i];
        
        
        
        set<ll> val;
        val.insert(0);
        rep(i,n)val.insert(p[i]);
        rep(i,n)for(ll j=i;j<n;j++)val.insert(p[i]+p[j]);
        
        vector<ll> left,right;
        
        for(auto &v : val) left.pb(v);
        
        
        sort(all(left));
        right = left;
        
        ll maxi=0;
        rep(i,left.size()){
            ll num = left[i];
            if(num>m)break;
            
            int pos = rev_lower_bound(right,m-num);
            
            maxi = max<ll>(maxi,num+right[pos]);
        }
        cout<<maxi<<endl;
    }
}

C++: #include <cstdio>
#include <cctype>
#include <utility>
#include <vector>
#include <algorithm>
#include <functional>
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);
		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.rbegin(), u.rend());
		u.erase(unique(u.begin(), u.end()), u.end());
		int r = 0;
		for (auto i = u.begin(), e = u.end(); i != e; i++) {
			e = lower_bound(i + 1, e, M - *i, greater<int>());
			r = max(r, *i + *e);
		}
		outl(r);
	}
}

C++: //http://judge.u-aizu.ac.jp/onlinejudge/review.jsp?rid=2676345#1
//http://judge.u-aizu.ac.jp/onlinejudge/review.jsp?rid=2676345#1
#include <iostream>
#include<cstdlib>
#include<queue>
#include<set>
#include<vector>
#include<string>
#include<algorithm>
#include<stack>
#include<map>
#include<cstdio>
#include<fstream>
#include<cstring>
using namespace std;
#define rep(i,a) for(int i=0;i<a;i++)
#define mp make_pair
#define P pair<int,int>
#define ll __int64

int n,m;
int t[10000];
const int MA=1000000;
int s1[MA],s2[MA];

int ya[4];

int main(){

while(cin>>n>>m,n||m){
rep(i,MA)s1[i]=s2[i]=0;
rep(i,10000)t[i]=0;
for(int i=1;i<=n;i++)cin>>t[i];
for(int i=0;i<=n;i++){
	for(int j=0;j<=n;j++){
		s1[i*(n+1)+j]=t[i]+t[j];
		s2[i*(n+1)+j]=t[i]+t[j];
	}
}
int g=(n+1)*(n+1);

sort(s1,s1+g);
sort(s2,s2+g);

//rep(i,g)cout<<s1[i]<<" ";cout<<endl;

int ans=0;

for(int i=0;i<g;i++){
	int now=s1[i];

	int l=0;
	int r=g-1;
	int mid=(l+r)/2;
	int x=s2[mid];

	for(int i=0;i<50;i++){
		if(x+now==m)break;
		if(x+now>m){
			r=mid;
			mid=(r+l)/2;
			x=s2[mid];
		}
		else{
			l=mid;
			mid=(r+l)/2;
			x=s2[mid];
		}
	}

	//cout<<" "<<x<<" "<<now<<" "<<x+now<<endl;
	if(x+now<=m)
	ans=max(ans,x+now);
}
cout<<ans<<endl;
}
	return 0;
}

C++: #include<iostream>
#include<set>
#include<vector>
using namespace std;
typedef unsigned int uint;
uint maxv;
void solve(uint now,uint m,uint *a,int n){
  int r=n-1,l=0,mid;
  while(l <=r){
    mid = (l+r)/2;
    if ( a[mid]+now>m)r=mid-1;
    else if ( a[mid]+now <m)l=mid+1;
    else break;

  }
  if ( now+a[mid]>maxv&& now+a[mid]<=m)maxv=now+a[mid];
}


main(){
  int n;
  uint m;
  while(scanf("%d%u",&n,&m) && n){
    set<uint> S;    
    uint one[n];
    uint two[n*n];
    int p=0;
    maxv=0;
    for(int i=0;i<n;i++)scanf("%d",&one[i]);
    for(int i=0;i<n;i++){
      if ( one[i]>maxv &&one[i] <=m)maxv=one[i];
      for(int j=i;j<n;j++){
	two[p++]=one[i]+one[j];
	if (two[p-1]>maxv&&two[p-1]<=m)maxv=two[p-1];
      }
    }
    sort(one,one+n);
    sort(two,two+p);
    for(int i=0;i<p;i++){
      //if ( two[i]+one[0]>m)break;
      //if ( two[i]+two[0]<=m)solve(two[i],m,two,p);
      //if ( two[i]+one[0]<=m)solve(two[i],m,one,n);
      solve(two[i],m,two,p);
      solve(two[i],m,one,n);
    }
    printf("%u\n",maxv);
  }
  return false;
}