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: Wrong Answer)

#include <bits/stdc++.h>

#define filein freopen ("in.txt", "r", stdin)
#define fileout freopen ("out.txt", "w", stdout)
#define dbg(x) cerr << #x << ": " << x << endl

using namespace std;
typedef long long ll;

const int maxn = 3005;

char s[maxn], t[maxn];
int slen, tlen;
ll dp[maxn][maxn];
string ans;

int main(){
	scanf ("%s%s", s, t);
	slen = strlen (s);
	tlen = strlen (t);
	for (int i = 1; i <= slen; i++){
		for (int j = 1; j <= tlen; j++){
			dp[i][j] = max (dp[i - 1][j], dp[i][j - 1]);
			if (s[i - 1] == t[j - 1])
				dp[i][j] = max (dp[i][j], 1 + dp[i - 1][j - 1]);
		}
	}
	int i = slen, j = tlen;
	while (dp[i][j]){
		if (dp[i][j] == 1 + dp[i - 1][j - 1]){
			ans += s[i - 1];
			i--;
			j--;
		}
		else if (dp[i][j] == dp[i - 1][j])
			i--;
		else
			j--;
	}
	for (int i = (int) ans.size() - 1; i >= 0; i--)
		cout << ans[i];
	cout << '\n';
	return 0;
}