
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {

		Scanner scanner = new Scanner(System.in);

		String s = scanner.nextLine();
		String t = scanner.nextLine();

		String[] ss = s.split("");
		String[] tt = t.split("");

		int count = 0;
		for (int i = 0; i < s.length(); i++) {

			if (!ss[i].equals(tt[i]) ) {
				ss[i] = tt[i];
				count++;
//				System.out.print(i+ " "+ss[i]+ " "+tt[i]);
			}

		}
		System.out.println(count);

	}

} import java.util.Scanner; Scanner java.util public class Main {

	public static void main(String[] args) {

		Scanner scanner = new Scanner(System.in);

		String s = scanner.nextLine();
		String t = scanner.nextLine();

		String[] ss = s.split("");
		String[] tt = t.split("");

		int count = 0;
		for (int i = 0; i < s.length(); i++) {

			if (!ss[i].equals(tt[i]) ) {
				ss[i] = tt[i];
				count++;
//				System.out.print(i+ " "+ss[i]+ " "+tt[i]);
			}

		}
		System.out.println(count);

	}

} Main public static void main(String[] args) {

		Scanner scanner = new Scanner(System.in);

		String s = scanner.nextLine();
		String t = scanner.nextLine();

		String[] ss = s.split("");
		String[] tt = t.split("");

		int count = 0;
		for (int i = 0; i < s.length(); i++) {

			if (!ss[i].equals(tt[i]) ) {
				ss[i] = tt[i];
				count++;
//				System.out.print(i+ " "+ss[i]+ " "+tt[i]);
			}

		}
		System.out.println(count);

	} main {

		Scanner scanner = new Scanner(System.in);

		String s = scanner.nextLine();
		String t = scanner.nextLine();

		String[] ss = s.split("");
		String[] tt = t.split("");

		int count = 0;
		for (int i = 0; i < s.length(); i++) {

			if (!ss[i].equals(tt[i]) ) {
				ss[i] = tt[i];
				count++;
//				System.out.print(i+ " "+ss[i]+ " "+tt[i]);
			}

		}
		System.out.println(count);

	} Scanner scanner = new Scanner(System.in); scanner new Scanner(System.in) String s = scanner.nextLine(); s scanner.nextLine() scanner.nextLine scanner String t = scanner.nextLine(); t scanner.nextLine() scanner.nextLine scanner String[] ss = s.split(""); ss s.split("") s.split s "" String[] tt = t.split(""); tt t.split("") t.split t "" int count = 0; count 0 for (int i = 0; i < s.length(); i++) {

			if (!ss[i].equals(tt[i]) ) {
				ss[i] = tt[i];
				count++;
//				System.out.print(i+ " "+ss[i]+ " "+tt[i]);
			}

		} int i = 0; int i = 0; i 0 i < s.length() i s.length() s.length s i++ i++ i {

			if (!ss[i].equals(tt[i]) ) {
				ss[i] = tt[i];
				count++;
//				System.out.print(i+ " "+ss[i]+ " "+tt[i]);
			}

		} {

			if (!ss[i].equals(tt[i]) ) {
				ss[i] = tt[i];
				count++;
//				System.out.print(i+ " "+ss[i]+ " "+tt[i]);
			}

		} if (!ss[i].equals(tt[i]) ) {
				ss[i] = tt[i];
				count++;
//				System.out.print(i+ " "+ss[i]+ " "+tt[i]);
			} !ss[i].equals(tt[i]) ss[i].equals(tt[i]) ss[i].equals ss[i] ss i tt[i] tt i {
				ss[i] = tt[i];
				count++;
//				System.out.print(i+ " "+ss[i]+ " "+tt[i]);
			} ss[i] = tt[i] ss[i] ss i tt[i] tt i 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 scanner = new Scanner(System.in);

		String s = scanner.nextLine();
		String t = scanner.nextLine();

		String[] ss = s.split("");
		String[] tt = t.split("");

		int count = 0;
		for (int i = 0; i < s.length(); i++) {

			if (!ss[i].equals(tt[i]) ) {
				ss[i] = tt[i];
				count++;
//				System.out.print(i+ " "+ss[i]+ " "+tt[i]);
			}

		}
		System.out.println(count);

	}

} public class Main {

	public static void main(String[] args) {

		Scanner scanner = new Scanner(System.in);

		String s = scanner.nextLine();
		String t = scanner.nextLine();

		String[] ss = s.split("");
		String[] tt = t.split("");

		int count = 0;
		for (int i = 0; i < s.length(); i++) {

			if (!ss[i].equals(tt[i]) ) {
				ss[i] = tt[i];
				count++;
//				System.out.print(i+ " "+ss[i]+ " "+tt[i]);
			}

		}
		System.out.println(count);

	}

} Main

import java.util.Scanner;

public class Main {

	public static void main(String[] args) {

		Scanner scanner = new Scanner(System.in);

		String s = scanner.nextLine();
		String t = scanner.nextLine();

		String[] ss = s.split("");
		String[] tt = t.split("");

		int count = 0;
		for (int i = 0; i < s.length(); i++) {

			if (!ss[i].equals(tt[i]) ) {
				ss[i] = tt[i];
				count++;
//				System.out.print(i+ " "+ss[i]+ " "+tt[i]);
			}

		}
		System.out.println(count);

	}

}
