import java.util.*;


public class Main {
    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        String S = sc.next();
		String T = sc.next();
      
      	String[] Sarray = S.split("");
      	String[] Tarray = T.split("");
      
      	int count = 0;
      	for (int i=0; i<Sarray.length; i++){
          	if (!Sarray[i].equals(Tarray[i])){
              	count += 1;
            }
        }
        
        System.out.println(count);
    }
} import java.util.*; util.* java public class Main {
    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        String S = sc.next();
		String T = sc.next();
      
      	String[] Sarray = S.split("");
      	String[] Tarray = T.split("");
      
      	int count = 0;
      	for (int i=0; i<Sarray.length; i++){
          	if (!Sarray[i].equals(Tarray[i])){
              	count += 1;
            }
        }
        
        System.out.println(count);
    }
} Main public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        String S = sc.next();
		String T = sc.next();
      
      	String[] Sarray = S.split("");
      	String[] Tarray = T.split("");
      
      	int count = 0;
      	for (int i=0; i<Sarray.length; i++){
          	if (!Sarray[i].equals(Tarray[i])){
              	count += 1;
            }
        }
        
        System.out.println(count);
    } main {

        Scanner sc = new Scanner(System.in);
        String S = sc.next();
		String T = sc.next();
      
      	String[] Sarray = S.split("");
      	String[] Tarray = T.split("");
      
      	int count = 0;
      	for (int i=0; i<Sarray.length; i++){
          	if (!Sarray[i].equals(Tarray[i])){
              	count += 1;
            }
        }
        
        System.out.println(count);
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) String S = sc.next(); S sc.next() sc.next sc String T = sc.next(); T sc.next() sc.next sc String[] Sarray = S.split(""); Sarray S.split("") S.split S "" String[] Tarray = T.split(""); Tarray T.split("") T.split T "" int count = 0; count 0 for (int i=0; i<Sarray.length; i++){
          	if (!Sarray[i].equals(Tarray[i])){
              	count += 1;
            }
        } int i=0; int i=0; i 0 i<Sarray.length i Sarray.length Sarray Sarray.length i++ i++ i {
          	if (!Sarray[i].equals(Tarray[i])){
              	count += 1;
            }
        } {
          	if (!Sarray[i].equals(Tarray[i])){
              	count += 1;
            }
        } if (!Sarray[i].equals(Tarray[i])){
              	count += 1;
            } !Sarray[i].equals(Tarray[i]) Sarray[i].equals(Tarray[i]) Sarray[i].equals Sarray[i] Sarray i Tarray[i] Tarray i {
              	count += 1;
            } count += 1 count 1 System.out.println(count) System.out.println System.out System System.out count String[] args args public class Main {
    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        String S = sc.next();
		String T = sc.next();
      
      	String[] Sarray = S.split("");
      	String[] Tarray = T.split("");
      
      	int count = 0;
      	for (int i=0; i<Sarray.length; i++){
          	if (!Sarray[i].equals(Tarray[i])){
              	count += 1;
            }
        }
        
        System.out.println(count);
    }
} public class Main {
    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        String S = sc.next();
		String T = sc.next();
      
      	String[] Sarray = S.split("");
      	String[] Tarray = T.split("");
      
      	int count = 0;
      	for (int i=0; i<Sarray.length; i++){
          	if (!Sarray[i].equals(Tarray[i])){
              	count += 1;
            }
        }
        
        System.out.println(count);
    }
} Main
import java.util.*;


public class Main {
    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        String S = sc.next();
		String T = sc.next();
      
      	String[] Sarray = S.split("");
      	String[] Tarray = T.split("");
      
      	int count = 0;
      	for (int i=0; i<Sarray.length; i++){
          	if (!Sarray[i].equals(Tarray[i])){
              	count += 1;
            }
        }
        
        System.out.println(count);
    }
}