

import java.util.Scanner;

public class Main {
    
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        
  String a=in.nextLine();
  String b=in.nextLine();
  int count=0;
        for (int i = 0; i <b.length(); i++) {
            if (a.charAt(i)!=b.charAt(i)) {
                count++;
                
            }
            
        }
        System.out.println(count);
  
   
    }
    
}
   

       import java.util.Scanner; Scanner java.util public class Main {
    
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        
  String a=in.nextLine();
  String b=in.nextLine();
  int count=0;
        for (int i = 0; i <b.length(); i++) {
            if (a.charAt(i)!=b.charAt(i)) {
                count++;
                
            }
            
        }
        System.out.println(count);
  
   
    }
    
} Main public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        
  String a=in.nextLine();
  String b=in.nextLine();
  int count=0;
        for (int i = 0; i <b.length(); i++) {
            if (a.charAt(i)!=b.charAt(i)) {
                count++;
                
            }
            
        }
        System.out.println(count);
  
   
    } main {
        Scanner in = new Scanner(System.in);
        
  String a=in.nextLine();
  String b=in.nextLine();
  int count=0;
        for (int i = 0; i <b.length(); i++) {
            if (a.charAt(i)!=b.charAt(i)) {
                count++;
                
            }
            
        }
        System.out.println(count);
  
   
    } Scanner in = new Scanner(System.in); in new Scanner(System.in) String a=in.nextLine(); a in.nextLine() in.nextLine in String b=in.nextLine(); b in.nextLine() in.nextLine in int count=0; count 0 for (int i = 0; i <b.length(); i++) {
            if (a.charAt(i)!=b.charAt(i)) {
                count++;
                
            }
            
        } int i = 0; int i = 0; i 0 i <b.length() i b.length() b.length b i++ i++ i {
            if (a.charAt(i)!=b.charAt(i)) {
                count++;
                
            }
            
        } {
            if (a.charAt(i)!=b.charAt(i)) {
                count++;
                
            }
            
        } if (a.charAt(i)!=b.charAt(i)) {
                count++;
                
            } a.charAt(i)!=b.charAt(i) a.charAt(i) a.charAt a i b.charAt(i) b.charAt b i {
                count++;
                
            } count++ count 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 in = new Scanner(System.in);
        
  String a=in.nextLine();
  String b=in.nextLine();
  int count=0;
        for (int i = 0; i <b.length(); i++) {
            if (a.charAt(i)!=b.charAt(i)) {
                count++;
                
            }
            
        }
        System.out.println(count);
  
   
    }
    
} public class Main {
    
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        
  String a=in.nextLine();
  String b=in.nextLine();
  int count=0;
        for (int i = 0; i <b.length(); i++) {
            if (a.charAt(i)!=b.charAt(i)) {
                count++;
                
            }
            
        }
        System.out.println(count);
  
   
    }
    
} Main


import java.util.Scanner;

public class Main {
    
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        
  String a=in.nextLine();
  String b=in.nextLine();
  int count=0;
        for (int i = 0; i <b.length(); i++) {
            if (a.charAt(i)!=b.charAt(i)) {
                count++;
                
            }
            
        }
        System.out.println(count);
  
   
    }
    
}
   

      
