import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		try(Scanner scanner = new Scanner(System.in)) {
			String data1 = scanner.nextLine();
			String data2 = scanner.nextLine();

			char[] s =  data1.toCharArray();
			char[] t =  data2.toCharArray();

			long count = 0;
			for (int i = 0; i < s.length; i++) {
				if (s[i] != t[i]) {
					count++;
				}
			}

			System.out.println(count);
		}
	}
} import java.util.Scanner; Scanner java.util public class Main {

	public static void main(String[] args) {
		try(Scanner scanner = new Scanner(System.in)) {
			String data1 = scanner.nextLine();
			String data2 = scanner.nextLine();

			char[] s =  data1.toCharArray();
			char[] t =  data2.toCharArray();

			long count = 0;
			for (int i = 0; i < s.length; i++) {
				if (s[i] != t[i]) {
					count++;
				}
			}

			System.out.println(count);
		}
	}
} Main public static void main(String[] args) {
		try(Scanner scanner = new Scanner(System.in)) {
			String data1 = scanner.nextLine();
			String data2 = scanner.nextLine();

			char[] s =  data1.toCharArray();
			char[] t =  data2.toCharArray();

			long count = 0;
			for (int i = 0; i < s.length; i++) {
				if (s[i] != t[i]) {
					count++;
				}
			}

			System.out.println(count);
		}
	} main {
		try(Scanner scanner = new Scanner(System.in)) {
			String data1 = scanner.nextLine();
			String data2 = scanner.nextLine();

			char[] s =  data1.toCharArray();
			char[] t =  data2.toCharArray();

			long count = 0;
			for (int i = 0; i < s.length; i++) {
				if (s[i] != t[i]) {
					count++;
				}
			}

			System.out.println(count);
		}
	} try(Scanner scanner = new Scanner(System.in)) {
			String data1 = scanner.nextLine();
			String data2 = scanner.nextLine();

			char[] s =  data1.toCharArray();
			char[] t =  data2.toCharArray();

			long count = 0;
			for (int i = 0; i < s.length; i++) {
				if (s[i] != t[i]) {
					count++;
				}
			}

			System.out.println(count);
		} {
			String data1 = scanner.nextLine();
			String data2 = scanner.nextLine();

			char[] s =  data1.toCharArray();
			char[] t =  data2.toCharArray();

			long count = 0;
			for (int i = 0; i < s.length; i++) {
				if (s[i] != t[i]) {
					count++;
				}
			}

			System.out.println(count);
		} Scanner scanner = new Scanner(System.in) Scanner scanner = new Scanner(System.in) new Scanner(System.in) String data1 = scanner.nextLine(); data1 scanner.nextLine() scanner.nextLine scanner String data2 = scanner.nextLine(); data2 scanner.nextLine() scanner.nextLine scanner char[] s =  data1.toCharArray(); s data1.toCharArray() data1.toCharArray data1 char[] t =  data2.toCharArray(); t data2.toCharArray() data2.toCharArray data2 long count = 0; count 0 for (int i = 0; i < s.length; i++) {
				if (s[i] != t[i]) {
					count++;
				}
			} int i = 0; int i = 0; i 0 i < s.length i s.length s s.length i++ i++ i {
				if (s[i] != t[i]) {
					count++;
				}
			} {
				if (s[i] != t[i]) {
					count++;
				}
			} if (s[i] != t[i]) {
					count++;
				} s[i] != t[i] s[i] s i t[i] t 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) {
		try(Scanner scanner = new Scanner(System.in)) {
			String data1 = scanner.nextLine();
			String data2 = scanner.nextLine();

			char[] s =  data1.toCharArray();
			char[] t =  data2.toCharArray();

			long count = 0;
			for (int i = 0; i < s.length; i++) {
				if (s[i] != t[i]) {
					count++;
				}
			}

			System.out.println(count);
		}
	}
} public class Main {

	public static void main(String[] args) {
		try(Scanner scanner = new Scanner(System.in)) {
			String data1 = scanner.nextLine();
			String data2 = scanner.nextLine();

			char[] s =  data1.toCharArray();
			char[] t =  data2.toCharArray();

			long count = 0;
			for (int i = 0; i < s.length; i++) {
				if (s[i] != t[i]) {
					count++;
				}
			}

			System.out.println(count);
		}
	}
} Main
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		try(Scanner scanner = new Scanner(System.in)) {
			String data1 = scanner.nextLine();
			String data2 = scanner.nextLine();

			char[] s =  data1.toCharArray();
			char[] t =  data2.toCharArray();

			long count = 0;
			for (int i = 0; i < s.length; i++) {
				if (s[i] != t[i]) {
					count++;
				}
			}

			System.out.println(count);
		}
	}
}