import java.util.Scanner;

public class Main {
	static Scanner sc = new Scanner(System.in);

	public static void main(String[] args) {
		String S = sc.nextLine();
		String T = sc.nextLine();
		int c = 0;
		for (int i = 0; i < S.length(); i++) {
			if (S.charAt(i) != T.charAt(i))
				c++;
		}
		System.out.println(c);
	}

} import java.util.Scanner; Scanner java.util public class Main {
	static Scanner sc = new Scanner(System.in);

	public static void main(String[] args) {
		String S = sc.nextLine();
		String T = sc.nextLine();
		int c = 0;
		for (int i = 0; i < S.length(); i++) {
			if (S.charAt(i) != T.charAt(i))
				c++;
		}
		System.out.println(c);
	}

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

	public static void main(String[] args) {
		String S = sc.nextLine();
		String T = sc.nextLine();
		int c = 0;
		for (int i = 0; i < S.length(); i++) {
			if (S.charAt(i) != T.charAt(i))
				c++;
		}
		System.out.println(c);
	}

} public class Main {
	static Scanner sc = new Scanner(System.in);

	public static void main(String[] args) {
		String S = sc.nextLine();
		String T = sc.nextLine();
		int c = 0;
		for (int i = 0; i < S.length(); i++) {
			if (S.charAt(i) != T.charAt(i))
				c++;
		}
		System.out.println(c);
	}

} Main
import java.util.Scanner;

public class Main {
	static Scanner sc = new Scanner(System.in);

	public static void main(String[] args) {
		String S = sc.nextLine();
		String T = sc.nextLine();
		int c = 0;
		for (int i = 0; i < S.length(); i++) {
			if (S.charAt(i) != T.charAt(i))
				c++;
		}
		System.out.println(c);
	}

}
