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 Rust (1.42.0) (judge verdict: Accepted)

#![allow(unused_imports)]
#![allow(unused_variables)]

use itertools::Itertools;
use proconio::{fastout, input};

#[fastout]
fn main() {
    input! {
        s1: String,
        s2: String,
    }
    // annotate for rust-analyzer
    let s1: Vec<char> = s1.chars().collect_vec();
    let s2: Vec<char> = s2.chars().collect_vec();

    let mut i = 0;
    let mut ans = 0;
    while i < s1.len() {
        if s1[i] != s2[i] {
            ans += 1;
        }
        i += 1;
    }

    println!("{}", ans);
}