import java.util.Arrays;
import java.util.Scanner;

public class Main {

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

		String a = sc.next();
		String b = sc.next();
		int count = 0;
		for (int i = 0; i < a.length(); i++) {
			if (a.charAt(i) != b.charAt(i)) {
				count++;
			}
		}
      
		System.out.println(count);
    }
} import java.util.Arrays; Arrays java.util import java.util.Scanner; Scanner java.util public class Main {

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

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

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

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

		String a = sc.next();
		String b = sc.next();
		int count = 0;
		for (int i = 0; i < a.length(); i++) {
			if (a.charAt(i) != b.charAt(i)) {
				count++;
			}
		}
      
		System.out.println(count);
    }
} public class Main {

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

		String a = sc.next();
		String b = sc.next();
		int count = 0;
		for (int i = 0; i < a.length(); i++) {
			if (a.charAt(i) != b.charAt(i)) {
				count++;
			}
		}
      
		System.out.println(count);
    }
} Main
import java.util.Arrays;
import java.util.Scanner;

public class Main {

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

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