import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String str1 = sc.next();
        String str2 = sc.next();
        int count = 0;
        for (int i = 0; i < str1.length(); i++) {
            count += str1.charAt(i) != str2.charAt(i) ? 1 : 0;
        }
        System.out.println(count);
    }
} import java.util.*; util.* java public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String str1 = sc.next();
        String str2 = sc.next();
        int count = 0;
        for (int i = 0; i < str1.length(); i++) {
            count += str1.charAt(i) != str2.charAt(i) ? 1 : 0;
        }
        System.out.println(count);
    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String str1 = sc.next();
        String str2 = sc.next();
        int count = 0;
        for (int i = 0; i < str1.length(); i++) {
            count += str1.charAt(i) != str2.charAt(i) ? 1 : 0;
        }
        System.out.println(count);
    } main {
        Scanner sc = new Scanner(System.in);
        String str1 = sc.next();
        String str2 = sc.next();
        int count = 0;
        for (int i = 0; i < str1.length(); i++) {
            count += str1.charAt(i) != str2.charAt(i) ? 1 : 0;
        }
        System.out.println(count);
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) String str1 = sc.next(); str1 sc.next() sc.next sc String str2 = sc.next(); str2 sc.next() sc.next sc int count = 0; count 0 for (int i = 0; i < str1.length(); i++) {
            count += str1.charAt(i) != str2.charAt(i) ? 1 : 0;
        } int i = 0; int i = 0; i 0 i < str1.length() i str1.length() str1.length str1 i++ i++ i {
            count += str1.charAt(i) != str2.charAt(i) ? 1 : 0;
        } {
            count += str1.charAt(i) != str2.charAt(i) ? 1 : 0;
        } count += str1.charAt(i) != str2.charAt(i) ? 1 : 0 count str1.charAt(i) != str2.charAt(i) ? 1 : 0 str1.charAt(i) != str2.charAt(i) str1.charAt(i) str1.charAt str1 i str2.charAt(i) str2.charAt str2 i 1 0 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 sc = new Scanner(System.in);
        String str1 = sc.next();
        String str2 = sc.next();
        int count = 0;
        for (int i = 0; i < str1.length(); i++) {
            count += str1.charAt(i) != str2.charAt(i) ? 1 : 0;
        }
        System.out.println(count);
    }
} public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String str1 = sc.next();
        String str2 = sc.next();
        int count = 0;
        for (int i = 0; i < str1.length(); i++) {
            count += str1.charAt(i) != str2.charAt(i) ? 1 : 0;
        }
        System.out.println(count);
    }
} Main
import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String str1 = sc.next();
        String str2 = sc.next();
        int count = 0;
        for (int i = 0; i < str1.length(); i++) {
            count += str1.charAt(i) != str2.charAt(i) ? 1 : 0;
        }
        System.out.println(count);
    }
}