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