LCS Common Subsequence

A subsequence of a given sequence is the given sequence with some elements (possible none) left out. Given a sequence X =

#include <iostream>
#include <algorithm>
#include <cstring>
using namespace std;
string X,Y;
int dp[1001][1001];
int main()
{
    while(cin>>X>>Y)
    {
        int len1=X.length();
        int len2=Y.length();
        for(int i=1;i<max(len1,len2);i++)
        {
            dp[0][i]=0;
            dp[i][0]=0;
        }
        for(int i=1;i<=len1;i++)
            for(int j=1;j<=len2;j++)
        {
            if(X[i-1]==Y[j-1])
                dp[i][j]=dp[i-1][j-1]+1;
            else
                dp[i][j]=max(dp[i][j-1],dp[i-1][j]);
        }
        cout<<dp[len1][len2]<<endl;
    }
    return 0;
}