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 C (GCC 9.2.1) (judge verdict: Runtime Error)

#include <stdio.h>
#include <ctype.h>

int main(){
    char s[200000];
    char t[200000];
    scanf("%s", s);
    scanf("%s", t);
    
    int cnt;

    for (int i = 0; s[i] != '\0' ; i++){
        char tmp;
        if ((s[i] != t[i]) && (isalpha(s[i])) && (isalpha(t[i]))){
            tmp = s[i];
            s[i] = t[i];
            t[i] = tmp;
            cnt++;
        }
    }
    
    printf("%d\n", cnt);
}