import java.util.Scanner;

public class Main
{
    public static void main(String[] args)
    {
        Scanner scanner = new Scanner(System.in);
        String s = scanner.nextLine();
        String t = scanner.nextLine();
        int counter = 0;
        
        for(int i = 1;i<=s.length();i++)
        {
            if(!s.substring(i-1,i).equals(t.substring(i-1,i)))
            {
                counter++;
            }
        }
        System.out.println(counter);
    }
} import java.util.Scanner; Scanner java.util public class Main
{
    public static void main(String[] args)
    {
        Scanner scanner = new Scanner(System.in);
        String s = scanner.nextLine();
        String t = scanner.nextLine();
        int counter = 0;
        
        for(int i = 1;i<=s.length();i++)
        {
            if(!s.substring(i-1,i).equals(t.substring(i-1,i)))
            {
                counter++;
            }
        }
        System.out.println(counter);
    }
} Main public static void main(String[] args)
    {
        Scanner scanner = new Scanner(System.in);
        String s = scanner.nextLine();
        String t = scanner.nextLine();
        int counter = 0;
        
        for(int i = 1;i<=s.length();i++)
        {
            if(!s.substring(i-1,i).equals(t.substring(i-1,i)))
            {
                counter++;
            }
        }
        System.out.println(counter);
    } main {
        Scanner scanner = new Scanner(System.in);
        String s = scanner.nextLine();
        String t = scanner.nextLine();
        int counter = 0;
        
        for(int i = 1;i<=s.length();i++)
        {
            if(!s.substring(i-1,i).equals(t.substring(i-1,i)))
            {
                counter++;
            }
        }
        System.out.println(counter);
    } Scanner scanner = new Scanner(System.in); scanner new Scanner(System.in) String s = scanner.nextLine(); s scanner.nextLine() scanner.nextLine scanner String t = scanner.nextLine(); t scanner.nextLine() scanner.nextLine scanner int counter = 0; counter 0 for(int i = 1;i<=s.length();i++)
        {
            if(!s.substring(i-1,i).equals(t.substring(i-1,i)))
            {
                counter++;
            }
        } int i = 1; int i = 1; i 1 i<=s.length() i s.length() s.length s i++ i++ i {
            if(!s.substring(i-1,i).equals(t.substring(i-1,i)))
            {
                counter++;
            }
        } {
            if(!s.substring(i-1,i).equals(t.substring(i-1,i)))
            {
                counter++;
            }
        } if(!s.substring(i-1,i).equals(t.substring(i-1,i)))
            {
                counter++;
            } !s.substring(i-1,i).equals(t.substring(i-1,i)) s.substring(i-1,i).equals(t.substring(i-1,i)) s.substring(i-1,i).equals s.substring(i-1,i) s.substring s i-1 i 1 i t.substring(i-1,i) t.substring t i-1 i 1 i {
                counter++;
            } counter++ counter System.out.println(counter) System.out.println System.out System System.out counter String[] args args public class Main
{
    public static void main(String[] args)
    {
        Scanner scanner = new Scanner(System.in);
        String s = scanner.nextLine();
        String t = scanner.nextLine();
        int counter = 0;
        
        for(int i = 1;i<=s.length();i++)
        {
            if(!s.substring(i-1,i).equals(t.substring(i-1,i)))
            {
                counter++;
            }
        }
        System.out.println(counter);
    }
} public class Main
{
    public static void main(String[] args)
    {
        Scanner scanner = new Scanner(System.in);
        String s = scanner.nextLine();
        String t = scanner.nextLine();
        int counter = 0;
        
        for(int i = 1;i<=s.length();i++)
        {
            if(!s.substring(i-1,i).equals(t.substring(i-1,i)))
            {
                counter++;
            }
        }
        System.out.println(counter);
    }
} Main
import java.util.Scanner;

public class Main
{
    public static void main(String[] args)
    {
        Scanner scanner = new Scanner(System.in);
        String s = scanner.nextLine();
        String t = scanner.nextLine();
        int counter = 0;
        
        for(int i = 1;i<=s.length();i++)
        {
            if(!s.substring(i-1,i).equals(t.substring(i-1,i)))
            {
                counter++;
            }
        }
        System.out.println(counter);
    }
}
