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>
#include<string.h>
int main(void)
{
    char s[200000];
    char t[200000];
    int i,cnt,len1,len2;
    cnt = 0;
	if(scanf("%s %s", s, t) < 2) {
      return 0;
    }
 	len1 = strlen(s);
 	len2 = strlen(t);
    if(len1 != len2){
        return 0;
    }
    for(i=0; i < len1; i++){
		if(!(s[i]>= 'a') && (s[i]<='z')){
          return 0;
        }
		if(!(t[i]>= 'a') && (t[i]<='z')){
          return 0;
        }
        if(s[i] != t[i]){
            cnt = cnt+1;
        }
    }
    printf("%d\n",cnt);
    return 0;
}