import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner c = new Scanner(System.in);

        String str1 = c.nextLine();
        String str2 = c.nextLine();
        int count = 0;

        for (int i = 0; i < str1.length(); i++) {
            if (!str1.substring(i, i + 1).equals(str2.substring(i, i + 1))) {
                count++;
            }
        }

        System.out.println(count);

    }

} import java.util.Scanner; Scanner java.util public class Main {

    public static void main(String[] args) {
        Scanner c = new Scanner(System.in);

        String str1 = c.nextLine();
        String str2 = c.nextLine();
        int count = 0;

        for (int i = 0; i < str1.length(); i++) {
            if (!str1.substring(i, i + 1).equals(str2.substring(i, i + 1))) {
                count++;
            }
        }

        System.out.println(count);

    }

} Main public static void main(String[] args) {
        Scanner c = new Scanner(System.in);

        String str1 = c.nextLine();
        String str2 = c.nextLine();
        int count = 0;

        for (int i = 0; i < str1.length(); i++) {
            if (!str1.substring(i, i + 1).equals(str2.substring(i, i + 1))) {
                count++;
            }
        }

        System.out.println(count);

    } main {
        Scanner c = new Scanner(System.in);

        String str1 = c.nextLine();
        String str2 = c.nextLine();
        int count = 0;

        for (int i = 0; i < str1.length(); i++) {
            if (!str1.substring(i, i + 1).equals(str2.substring(i, i + 1))) {
                count++;
            }
        }

        System.out.println(count);

    } Scanner c = new Scanner(System.in); c new Scanner(System.in) String str1 = c.nextLine(); str1 c.nextLine() c.nextLine c String str2 = c.nextLine(); str2 c.nextLine() c.nextLine c int count = 0; count 0 for (int i = 0; i < str1.length(); i++) {
            if (!str1.substring(i, i + 1).equals(str2.substring(i, i + 1))) {
                count++;
            }
        } int i = 0; int i = 0; i 0 i < str1.length() i str1.length() str1.length str1 i++ i++ i {
            if (!str1.substring(i, i + 1).equals(str2.substring(i, i + 1))) {
                count++;
            }
        } {
            if (!str1.substring(i, i + 1).equals(str2.substring(i, i + 1))) {
                count++;
            }
        } if (!str1.substring(i, i + 1).equals(str2.substring(i, i + 1))) {
                count++;
            } !str1.substring(i, i + 1).equals(str2.substring(i, i + 1)) str1.substring(i, i + 1).equals(str2.substring(i, i + 1)) str1.substring(i, i + 1).equals str1.substring(i, i + 1) str1.substring str1 i i + 1 i 1 str2.substring(i, i + 1) str2.substring str2 i i + 1 i 1 {
                count++;
            } 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 c = new Scanner(System.in);

        String str1 = c.nextLine();
        String str2 = c.nextLine();
        int count = 0;

        for (int i = 0; i < str1.length(); i++) {
            if (!str1.substring(i, i + 1).equals(str2.substring(i, i + 1))) {
                count++;
            }
        }

        System.out.println(count);

    }

} public class Main {

    public static void main(String[] args) {
        Scanner c = new Scanner(System.in);

        String str1 = c.nextLine();
        String str2 = c.nextLine();
        int count = 0;

        for (int i = 0; i < str1.length(); i++) {
            if (!str1.substring(i, i + 1).equals(str2.substring(i, i + 1))) {
                count++;
            }
        }

        System.out.println(count);

    }

} Main
import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner c = new Scanner(System.in);

        String str1 = c.nextLine();
        String str2 = c.nextLine();
        int count = 0;

        for (int i = 0; i < str1.length(); i++) {
            if (!str1.substring(i, i + 1).equals(str2.substring(i, i + 1))) {
                count++;
            }
        }

        System.out.println(count);

    }

}