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 <string.h>

int main(){
	
	char a[20000];
    char b[20000];
  	int i;
  	int n = 0;
	if(scanf("%s",a) == -1){
    	return 0;
    }
	if(scanf("%s",b) == -1){
    	return 0;
    }
  	for(i=0;i<20000;i++){
        if(a[i]=='\0'&&b[i] == '\0'){
      break;
    }
      
	if(strncmp(&a[i],&b[i],1)!=0){
      n = n+1;
    }

    }
  
	printf("%d\n",n);
	
	return 0;
}