import java.util.*;

class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    String str01 = sc.next();
    String str02 = sc.next();
    
    int count = 0;
    if(str01.equals(str02)){
    	System.out.println(count);
    }else{
    	for(int i = 0; i < str01.length(); i++){
        	if(str01.charAt(i) != str02.charAt(i)){
		 		count++;
            }
        }
      System.out.println(count);
    }
    
  }
} import java.util.*; util.* java class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    String str01 = sc.next();
    String str02 = sc.next();
    
    int count = 0;
    if(str01.equals(str02)){
    	System.out.println(count);
    }else{
    	for(int i = 0; i < str01.length(); i++){
        	if(str01.charAt(i) != str02.charAt(i)){
		 		count++;
            }
        }
      System.out.println(count);
    }
    
  }
} Main public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    String str01 = sc.next();
    String str02 = sc.next();
    
    int count = 0;
    if(str01.equals(str02)){
    	System.out.println(count);
    }else{
    	for(int i = 0; i < str01.length(); i++){
        	if(str01.charAt(i) != str02.charAt(i)){
		 		count++;
            }
        }
      System.out.println(count);
    }
    
  } main {
    Scanner sc = new Scanner(System.in);
    String str01 = sc.next();
    String str02 = sc.next();
    
    int count = 0;
    if(str01.equals(str02)){
    	System.out.println(count);
    }else{
    	for(int i = 0; i < str01.length(); i++){
        	if(str01.charAt(i) != str02.charAt(i)){
		 		count++;
            }
        }
      System.out.println(count);
    }
    
  } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) String str01 = sc.next(); str01 sc.next() sc.next sc String str02 = sc.next(); str02 sc.next() sc.next sc int count = 0; count 0 if(str01.equals(str02)){
    	System.out.println(count);
    }else{
    	for(int i = 0; i < str01.length(); i++){
        	if(str01.charAt(i) != str02.charAt(i)){
		 		count++;
            }
        }
      System.out.println(count);
    } str01.equals(str02) str01.equals str01 str02 {
    	System.out.println(count);
    } System.out.println(count) System.out.println System.out System System.out count {
    	for(int i = 0; i < str01.length(); i++){
        	if(str01.charAt(i) != str02.charAt(i)){
		 		count++;
            }
        }
      System.out.println(count);
    } for(int i = 0; i < str01.length(); i++){
        	if(str01.charAt(i) != str02.charAt(i)){
		 		count++;
            }
        } int i = 0; int i = 0; i 0 i < str01.length() i str01.length() str01.length str01 i++ i++ i {
        	if(str01.charAt(i) != str02.charAt(i)){
		 		count++;
            }
        } {
        	if(str01.charAt(i) != str02.charAt(i)){
		 		count++;
            }
        } if(str01.charAt(i) != str02.charAt(i)){
		 		count++;
            } str01.charAt(i) != str02.charAt(i) str01.charAt(i) str01.charAt str01 i str02.charAt(i) str02.charAt str02 i {
		 		count++;
            } count++ count System.out.println(count) System.out.println System.out System System.out count String[] args args
import java.util.*;

class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    String str01 = sc.next();
    String str02 = sc.next();
    
    int count = 0;
    if(str01.equals(str02)){
    	System.out.println(count);
    }else{
    	for(int i = 0; i < str01.length(); i++){
        	if(str01.charAt(i) != str02.charAt(i)){
		 		count++;
            }
        }
      System.out.println(count);
    }
    
  }
}