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

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

        String a = sc.next();
        String b = sc.next();

        int n = a.length();
        int ans = 0;

        for (int i = 0; i<n; i++){
            if (a.charAt(i) != b.charAt(i)){
                ans++;
            }
        }
        System.out.println(ans);
    }
} import java.util.*; util.* java import java.io.*; io.* java import java.lang.*; lang.* java public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        String a = sc.next();
        String b = sc.next();

        int n = a.length();
        int ans = 0;

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

        String a = sc.next();
        String b = sc.next();

        int n = a.length();
        int ans = 0;

        for (int i = 0; i<n; i++){
            if (a.charAt(i) != b.charAt(i)){
                ans++;
            }
        }
        System.out.println(ans);
    } main {
        Scanner sc = new Scanner(System.in);

        String a = sc.next();
        String b = sc.next();

        int n = a.length();
        int ans = 0;

        for (int i = 0; i<n; i++){
            if (a.charAt(i) != b.charAt(i)){
                ans++;
            }
        }
        System.out.println(ans);
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) String a = sc.next(); a sc.next() sc.next sc String b = sc.next(); b sc.next() sc.next sc int n = a.length(); n a.length() a.length a int ans = 0; ans 0 for (int i = 0; i<n; i++){
            if (a.charAt(i) != b.charAt(i)){
                ans++;
            }
        } int i = 0; int i = 0; i 0 i<n i n i++ i++ i {
            if (a.charAt(i) != b.charAt(i)){
                ans++;
            }
        } {
            if (a.charAt(i) != b.charAt(i)){
                ans++;
            }
        } if (a.charAt(i) != b.charAt(i)){
                ans++;
            } a.charAt(i) != b.charAt(i) a.charAt(i) a.charAt a i b.charAt(i) b.charAt b 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 a = sc.next();
        String b = sc.next();

        int n = a.length();
        int ans = 0;

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

        String a = sc.next();
        String b = sc.next();

        int n = a.length();
        int ans = 0;

        for (int i = 0; i<n; i++){
            if (a.charAt(i) != b.charAt(i)){
                ans++;
            }
        }
        System.out.println(ans);
    }
} Main
import java.util.*;
import java.io.*;
import java.lang.*;

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

        String a = sc.next();
        String b = sc.next();

        int n = a.length();
        int ans = 0;

        for (int i = 0; i<n; i++){
            if (a.charAt(i) != b.charAt(i)){
                ans++;
            }
        }
        System.out.println(ans);
    }
}