import java.lang.*;
import java.util.*;

public class Main{
  public static void main(String[] args){
    Scanner scan = new Scanner(System.in);
    String s1 = scan.nextLine();
    String s2 = scan.nextLine();
    
   	int count = 0;
    
    if(!s1.equals(s2)){
      for(int i = 0; i < s1.length(); i++){
        if(s1.charAt(i) != s2.charAt(i)) count++;
      }
    }
    
    System.out.println(count);
  }
} import java.lang.*; lang.* java import java.util.*; util.* java public class Main{
  public static void main(String[] args){
    Scanner scan = new Scanner(System.in);
    String s1 = scan.nextLine();
    String s2 = scan.nextLine();
    
   	int count = 0;
    
    if(!s1.equals(s2)){
      for(int i = 0; i < s1.length(); i++){
        if(s1.charAt(i) != s2.charAt(i)) count++;
      }
    }
    
    System.out.println(count);
  }
} Main public static void main(String[] args){
    Scanner scan = new Scanner(System.in);
    String s1 = scan.nextLine();
    String s2 = scan.nextLine();
    
   	int count = 0;
    
    if(!s1.equals(s2)){
      for(int i = 0; i < s1.length(); i++){
        if(s1.charAt(i) != s2.charAt(i)) count++;
      }
    }
    
    System.out.println(count);
  } main {
    Scanner scan = new Scanner(System.in);
    String s1 = scan.nextLine();
    String s2 = scan.nextLine();
    
   	int count = 0;
    
    if(!s1.equals(s2)){
      for(int i = 0; i < s1.length(); i++){
        if(s1.charAt(i) != s2.charAt(i)) count++;
      }
    }
    
    System.out.println(count);
  } Scanner scan = new Scanner(System.in); scan new Scanner(System.in) String s1 = scan.nextLine(); s1 scan.nextLine() scan.nextLine scan String s2 = scan.nextLine(); s2 scan.nextLine() scan.nextLine scan int count = 0; count 0 if(!s1.equals(s2)){
      for(int i = 0; i < s1.length(); i++){
        if(s1.charAt(i) != s2.charAt(i)) count++;
      }
    } !s1.equals(s2) s1.equals(s2) s1.equals s1 s2 {
      for(int i = 0; i < s1.length(); i++){
        if(s1.charAt(i) != s2.charAt(i)) count++;
      }
    } for(int i = 0; i < s1.length(); i++){
        if(s1.charAt(i) != s2.charAt(i)) count++;
      } int i = 0; int i = 0; i 0 i < s1.length() i s1.length() s1.length s1 i++ i++ i {
        if(s1.charAt(i) != s2.charAt(i)) count++;
      } {
        if(s1.charAt(i) != s2.charAt(i)) count++;
      } if(s1.charAt(i) != s2.charAt(i)) count++; s1.charAt(i) != s2.charAt(i) s1.charAt(i) s1.charAt s1 i s2.charAt(i) s2.charAt s2 i 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 scan = new Scanner(System.in);
    String s1 = scan.nextLine();
    String s2 = scan.nextLine();
    
   	int count = 0;
    
    if(!s1.equals(s2)){
      for(int i = 0; i < s1.length(); i++){
        if(s1.charAt(i) != s2.charAt(i)) count++;
      }
    }
    
    System.out.println(count);
  }
} public class Main{
  public static void main(String[] args){
    Scanner scan = new Scanner(System.in);
    String s1 = scan.nextLine();
    String s2 = scan.nextLine();
    
   	int count = 0;
    
    if(!s1.equals(s2)){
      for(int i = 0; i < s1.length(); i++){
        if(s1.charAt(i) != s2.charAt(i)) count++;
      }
    }
    
    System.out.println(count);
  }
} Main
import java.lang.*;
import java.util.*;

public class Main{
  public static void main(String[] args){
    Scanner scan = new Scanner(System.in);
    String s1 = scan.nextLine();
    String s2 = scan.nextLine();
    
   	int count = 0;
    
    if(!s1.equals(s2)){
      for(int i = 0; i < s1.length(); i++){
        if(s1.charAt(i) != s2.charAt(i)) count++;
      }
    }
    
    System.out.println(count);
  }
}
