import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String s = sc.next();
        String t = sc.next();
        int ans = 0;
        for (int i = 0; i < s.length(); i++) {
            if (s.charAt(i) != t.charAt(i)) {
                ans++;
            }
        }
        System.out.println(ans);
    }

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

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String s = sc.next();
        String t = sc.next();
        int ans = 0;
        for (int i = 0; i < s.length(); i++) {
            if (s.charAt(i) != t.charAt(i)) {
                ans++;
            }
        }
        System.out.println(ans);
    }

} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String s = sc.next();
        String t = sc.next();
        int ans = 0;
        for (int i = 0; i < s.length(); i++) {
            if (s.charAt(i) != t.charAt(i)) {
                ans++;
            }
        }
        System.out.println(ans);
    } main {
        Scanner sc = new Scanner(System.in);
        String s = sc.next();
        String t = sc.next();
        int ans = 0;
        for (int i = 0; i < s.length(); i++) {
            if (s.charAt(i) != t.charAt(i)) {
                ans++;
            }
        }
        System.out.println(ans);
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) String s = sc.next(); s sc.next() sc.next sc String t = sc.next(); t sc.next() sc.next sc int ans = 0; ans 0 for (int i = 0; i < s.length(); i++) {
            if (s.charAt(i) != t.charAt(i)) {
                ans++;
            }
        } int i = 0; int i = 0; i 0 i < s.length() i s.length() s.length s i++ i++ i {
            if (s.charAt(i) != t.charAt(i)) {
                ans++;
            }
        } {
            if (s.charAt(i) != t.charAt(i)) {
                ans++;
            }
        } if (s.charAt(i) != t.charAt(i)) {
                ans++;
            } s.charAt(i) != t.charAt(i) s.charAt(i) s.charAt s i t.charAt(i) t.charAt t i {
                ans++;
            } ans++ ans System.out.println(ans) System.out.println System.out System System.out ans String[] args args public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String s = sc.next();
        String t = sc.next();
        int ans = 0;
        for (int i = 0; i < s.length(); i++) {
            if (s.charAt(i) != t.charAt(i)) {
                ans++;
            }
        }
        System.out.println(ans);
    }

} public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String s = sc.next();
        String t = sc.next();
        int ans = 0;
        for (int i = 0; i < s.length(); i++) {
            if (s.charAt(i) != t.charAt(i)) {
                ans++;
            }
        }
        System.out.println(ans);
    }

} Main
import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String s = sc.next();
        String t = sc.next();
        int ans = 0;
        for (int i = 0; i < s.length(); i++) {
            if (s.charAt(i) != t.charAt(i)) {
                ans++;
            }
        }
        System.out.println(ans);
    }

}
