import java.util.Scanner;


class Main{
 public static void main(String args[]){
   Scanner sc = new Scanner(System.in);
   String s = sc.next();
   String t = sc.next();
   int count=0;
   
   for(int i=0;i<s.length();i++){
    if((s.charAt(i))==(t.charAt(i))){
   count++;
    }
   }

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

   
     System.out.println(s.length()-count);
   
 
 }
} Main public static void main(String args[]){
   Scanner sc = new Scanner(System.in);
   String s = sc.next();
   String t = sc.next();
   int count=0;
   
   for(int i=0;i<s.length();i++){
    if((s.charAt(i))==(t.charAt(i))){
   count++;
    }
   }

   
     System.out.println(s.length()-count);
   
 
 } main {
   Scanner sc = new Scanner(System.in);
   String s = sc.next();
   String t = sc.next();
   int count=0;
   
   for(int i=0;i<s.length();i++){
    if((s.charAt(i))==(t.charAt(i))){
   count++;
    }
   }

   
     System.out.println(s.length()-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 int count=0; count 0 for(int i=0;i<s.length();i++){
    if((s.charAt(i))==(t.charAt(i))){
   count++;
    }
   } 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))){
   count++;
    }
   } {
    if((s.charAt(i))==(t.charAt(i))){
   count++;
    }
   } if((s.charAt(i))==(t.charAt(i))){
   count++;
    } (s.charAt(i))==(t.charAt(i)) (s.charAt(i)) s.charAt s i (t.charAt(i)) t.charAt t i {
   count++;
    } count++ count System.out.println(s.length()-count) System.out.println System.out System System.out s.length()-count s.length() s.length s count String args[] args
import java.util.Scanner;


class Main{
 public static void main(String args[]){
   Scanner sc = new Scanner(System.in);
   String s = sc.next();
   String t = sc.next();
   int count=0;
   
   for(int i=0;i<s.length();i++){
    if((s.charAt(i))==(t.charAt(i))){
   count++;
    }
   }

   
     System.out.println(s.length()-count);
   
 
 }
}
