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)

use std::io;

fn main() {
    let mut buf = String::new();
    io::stdin().read_line(&mut buf).expect("");
    let mut s = buf.trim().chars();
    
    let mut buf = String::new();
    io::stdin().read_line(&mut buf).expect("");
    let mut t = buf.trim().chars();
    let mut cnt:u32 = 0;
    
    for i in 0..s.clone().count() {
        if s.next() != t.next() {
            cnt += 1;
        }
    }
    println!("{}", cnt);
}