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: Wrong Answer)

#include <stdio.h>
#define MAX 20000
#include <string.h>
int main()
{
	char str1[MAX], str2[MAX];
	int count = 0, n = 0;
	
	fgets(str1,sizeof(str1),stdin);
	fgets(str2,sizeof(str2),stdin);
	
	for (int i = 0, n = strlen(str1) - 1; i < n; i++)
	{
		if (str1[i] != str2[i])
		{
			count++;
		}
	}
	printf("%d\n", count);
	return 0;
}