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>
#define warn_unused_result

int main (void){
  
  int i,count = 0;
  char S[20],T[20];
  
  (void)scanf("%s",S);
  
  (void)scanf("%s",T);
  
  if((strlen(S)<1 || strlen(S)>200000) || (strlen(T)<1 || strlen(T)>200000)){
    return 1; 
  }
  
  if(strlen(S) != strlen(T)){
    return 1;
  }
  
  for(i=0;(i<strlen(S))&&(i<strlen(T));i++)
  if((S[i]<'a' || S[i]>'z') || (T[i]<'a' || T[i]>'z')){
    return 1;
  }
  
  for(i=0;i<strlen(S);i++){
    if(S[i] != T[i]){
      count ++;
    }
  }
             
  printf("%d",count);
  
  return 0;
  
}