Problem:
Score : 100 points

Problem Statement

You are given strings s and t.
Find one longest string that is a subsequence of both s and t.

Notes

A subsequence of a string x is the string obtained by removing zero or more characters from x and concatenating the remaining characters without changing the order.

Constraints

s and t are strings consisting of lowercase English letters.

1 \leq |s|, |t| \leq 3000

Input

Input is given from Standard Input in the following format:

s
t

Output

Print one longest string that is a subsequence of both s and t.
If there are multiple such strings, any of them will be accepted.

Sample Input 1

axyb
abyxb

Sample Output 1

axb

The answer is axb or ayb; either will be accepted.

Sample Input 2

aa
xayaz

Sample Output 2

aa

Sample Input 3

a
z

Sample Output 3

The answer is (an empty string).

Sample Input 4

abracadabra
avadakedavra

Sample Output 4

aaadara

Solution in C++14 (GCC 5.4.1) (judge verdict: Accepted)

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

const int maxn=3010;
char a[maxn],b[maxn];
int dp[maxn][maxn];
int l1,l2;

void rek(int i, int j)
{
	if(i==0 || j==0)
		return;
	if(dp[i-1][j-1]+1==dp[i][j] && a[i]==b[j])
		{ rek(i-1,j-1); printf("%c",a[i]); }
	else
		{ (dp[i-1][j]>dp[i][j-1]) ? rek(i-1,j) : rek(i,j-1);  }
}

int main()
{
	scanf("%s",a+1);
	scanf("%s",b+1);
	l1=strlen(a+1); l2=strlen(b+1);
	for(int i=1;i<=l1;i++)
	{
		for(int j=1;j<=l2;j++)
		{
			dp[i][j]=max(dp[i][j-1],dp[i-1][j]);
			if(a[i]==b[j])
				dp[i][j]=max(dp[i][j],dp[i-1][j-1]+1);
		}
	}
	rek(l1,l2);
}