Problem:
Score : 200 points

Problem Statement

Given are strings S and T. Consider changing S to T by repeating the operation below. Find the minimum number of operations required to do so.

Operation: Choose one character of S and replace it with a different character.

Constraints

S and T have lengths between 1 and 2\times 10^5 (inclusive).

S and T consists of lowercase English letters.

S and T have equal lengths.

Input

Input is given from Standard Input in the following format:

S
T

Output

Print the answer.

Sample Input 1

cupofcoffee
cupofhottea

Sample Output 1

4

We can achieve the objective in four operations, such as the following:

First, replace the sixth character c with h.

Second, replace the eighth character f with t.

Third, replace the ninth character f with t.

Fourth, replace the eleventh character e with a.

Sample Input 2

abcde
bcdea

Sample Output 2

5

Sample Input 3

apple
apple

Sample Output 3

0

No operations may be needed to achieve the objective.

Solution in Java (OpenJDK 11.0.6) (judge verdict: Accepted)

import java.util.Scanner;

public class Main {
    public static int distance(String s1, String s2, int i, int j) {
        if (j == s2.length()) {
            return s1.length() - i;
        }
        if (i == s1.length()) {
            return s2.length() - j;
        }
        if (s1.charAt(i) == s2.charAt(j)) {
            return distance(s1, s2, i + 1, j + 1);
        }
        int rep = distance(s1, s2, i + 1, j + 1) + 1;
        return rep;
    }

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int dist = distance(in.next(), in.next(), 0, 0);
        System.out.println(dist);

    }

}