import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		try (Scanner sc = new Scanner(System.in)) {
            char[] c1 = sc.nextLine().toCharArray();
            char[] c2 = sc.nextLine().toCharArray();

            int len = c1.length;
            int counter = 0;

            for (int i = 0; i < len; i++) {
            	if  (c1[i] != c2[i]) counter++;
            }



            System.out.println(counter);

		} catch (Exception e) {
			// TODO: handle exception
		}
	}
} import java.util.Scanner; Scanner java.util public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		try (Scanner sc = new Scanner(System.in)) {
            char[] c1 = sc.nextLine().toCharArray();
            char[] c2 = sc.nextLine().toCharArray();

            int len = c1.length;
            int counter = 0;

            for (int i = 0; i < len; i++) {
            	if  (c1[i] != c2[i]) counter++;
            }



            System.out.println(counter);

		} catch (Exception e) {
			// TODO: handle exception
		}
	}
} Main public static void main(String[] args) {
		// TODO Auto-generated method stub
		try (Scanner sc = new Scanner(System.in)) {
            char[] c1 = sc.nextLine().toCharArray();
            char[] c2 = sc.nextLine().toCharArray();

            int len = c1.length;
            int counter = 0;

            for (int i = 0; i < len; i++) {
            	if  (c1[i] != c2[i]) counter++;
            }



            System.out.println(counter);

		} catch (Exception e) {
			// TODO: handle exception
		}
	} main {
		// TODO Auto-generated method stub
		try (Scanner sc = new Scanner(System.in)) {
            char[] c1 = sc.nextLine().toCharArray();
            char[] c2 = sc.nextLine().toCharArray();

            int len = c1.length;
            int counter = 0;

            for (int i = 0; i < len; i++) {
            	if  (c1[i] != c2[i]) counter++;
            }



            System.out.println(counter);

		} catch (Exception e) {
			// TODO: handle exception
		}
	} try (Scanner sc = new Scanner(System.in)) {
            char[] c1 = sc.nextLine().toCharArray();
            char[] c2 = sc.nextLine().toCharArray();

            int len = c1.length;
            int counter = 0;

            for (int i = 0; i < len; i++) {
            	if  (c1[i] != c2[i]) counter++;
            }



            System.out.println(counter);

		} catch (Exception e) {
			// TODO: handle exception
		} catch (Exception e) {
			// TODO: handle exception
		} Exception e {
			// TODO: handle exception
		} {
            char[] c1 = sc.nextLine().toCharArray();
            char[] c2 = sc.nextLine().toCharArray();

            int len = c1.length;
            int counter = 0;

            for (int i = 0; i < len; i++) {
            	if  (c1[i] != c2[i]) counter++;
            }



            System.out.println(counter);

		} Scanner sc = new Scanner(System.in) Scanner sc = new Scanner(System.in) new Scanner(System.in) char[] c1 = sc.nextLine().toCharArray(); c1 sc.nextLine().toCharArray() sc.nextLine().toCharArray sc.nextLine() sc.nextLine sc char[] c2 = sc.nextLine().toCharArray(); c2 sc.nextLine().toCharArray() sc.nextLine().toCharArray sc.nextLine() sc.nextLine sc int len = c1.length; len c1.length c1 c1.length int counter = 0; counter 0 for (int i = 0; i < len; i++) {
            	if  (c1[i] != c2[i]) counter++;
            } int i = 0; int i = 0; i 0 i < len i len i++ i++ i {
            	if  (c1[i] != c2[i]) counter++;
            } {
            	if  (c1[i] != c2[i]) counter++;
            } if  (c1[i] != c2[i]) counter++; c1[i] != c2[i] c1[i] c1 i c2[i] c2 i 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) {
		// TODO Auto-generated method stub
		try (Scanner sc = new Scanner(System.in)) {
            char[] c1 = sc.nextLine().toCharArray();
            char[] c2 = sc.nextLine().toCharArray();

            int len = c1.length;
            int counter = 0;

            for (int i = 0; i < len; i++) {
            	if  (c1[i] != c2[i]) counter++;
            }



            System.out.println(counter);

		} catch (Exception e) {
			// TODO: handle exception
		}
	}
} public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		try (Scanner sc = new Scanner(System.in)) {
            char[] c1 = sc.nextLine().toCharArray();
            char[] c2 = sc.nextLine().toCharArray();

            int len = c1.length;
            int counter = 0;

            for (int i = 0; i < len; i++) {
            	if  (c1[i] != c2[i]) counter++;
            }



            System.out.println(counter);

		} catch (Exception e) {
			// TODO: handle exception
		}
	}
} Main
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		try (Scanner sc = new Scanner(System.in)) {
            char[] c1 = sc.nextLine().toCharArray();
            char[] c2 = sc.nextLine().toCharArray();

            int len = c1.length;
            int counter = 0;

            for (int i = 0; i < len; i++) {
            	if  (c1[i] != c2[i]) counter++;
            }



            System.out.println(counter);

		} catch (Exception e) {
			// TODO: handle exception
		}
	}
}