Problem: Iroha has a sequence of N strings s_1, s_2, ..., s_N.

She will choose some (possibly all) strings from the sequence, then concatenate those strings retaining the relative order, to produce a long string.

Among all strings of length K that she can produce in this way, find the lexicographically smallest one.

Constraints

* 1 ≦ N ≦ 2000
* 1 ≦ K ≦ 10^4
* For each i, 1 ≦ |s_i| ≦ K.
* |s_1| + |s_2| + ... + |s_N| ≦ 10^6
* For each i, s_i consists of lowercase letters.
* There exists at least one string of length K that Iroha can produce.

Input

The input is given from Standard Input in the following format:


N K
s_1
s_2
:
s_N


Output

Print the lexicographically smallest string of length K that Iroha can produce.

Examples

Input

3 7
at
coder
codar


Output

atcodar


Input

3 7
coder
codar
at


Output

codarat


Input

4 13
kyuri
namida
zzzzzzz
aaaaaa


Output

namidazzzzzzz

Solution (in CPP):

Solution:
#include<cstdio>
#include<iostream>
#include<cstring>
#include<bitset>
#define mp(a,b) make_pair(a,b)
using namespace std;
bitset<10010> can[2010];
pair<int,int> vis[2][10010];
char s[2010][20010],ans[1000010];
int len[2010],n,k,cnt,ncnt;
int main()
{
	scanf("%d%d",&n,&k);
	for (int i=1;i<=n;i++) scanf("%s",s[i]),len[i]=strlen(s[i]);
	can[n+1][0]=1;
	for (int i=n;i>=1;i--)
		can[i]=can[i+1]|(can[i+1]<<len[i]);
	for (int i=1;i<=n;i++)
		if (can[i+1][k-len[i]]) vis[0][++cnt]=mp(i,0);
	int ii=0;
	for (int i=0;i<k;i++)
	{
		char minc='z';
		for (int j=1;j<=cnt;j++) minc=min(minc,s[vis[ii][j].first][vis[ii][j].second]);
		ans[i]=minc;
		int minid=n+1;
		ncnt=0;
		for (int j=1;j<=cnt;j++)
		{
			int nid=vis[ii][j].first,nlen=vis[ii][j].second;
			if (s[nid][nlen]!=minc) continue;
			if (nlen+1==len[nid]) minid=min(minid,nid);
			else vis[ii^1][++ncnt]=mp(nid,nlen+1);
		}
		for (int j=minid+1;j<=n;j++)
			if (k-len[j]-i-1>=0&&can[j+1][k-len[j]-i-1]) vis[ii^1][++ncnt]=mp(j,0);
		ii^=1;
		cnt=ncnt;
	}
	printf("%s",ans);
}