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