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 occurence_change(char*s,char*t){
    int cnt = 0;
    for(int i = 0; i <20000;i++){
            if(s[i]=='\0') break;
            if(s[i]!=t[i])cnt++;
        }
    return cnt;
}

int main(int argc,char*argv[]){
    char s[200000];
    char t[200000];
    strcpy(s,"cupofcoffee");
    strcpy(t,"cupofhottea");
    printf("%d\n",occurence_change(s,t));
    return 0;
}