public static int commonChild(String s1, String s2) {
    // Write your code here
    int[][] dp = new int[5001][5001];
    for (int i = 0; i < s1.length(); i++){
        for (int j = 0; j < s2.length(); j++){
            if (s1.charAt(i) == s2.charAt(j)){
                dp[i+1][j+1] = dp[i][j]+1;
                
            }
            else{
                dp[i+1][j+1] = Math.max(dp[i][j+1],dp[i+1][j]);
            }
            
        }
    }
    return dp[s1.length()][s2.length()];
    }