import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		String s = scan.nextLine();
		String t = scan.nextLine();
		scan.close();
		int count = 0;
		for (int i = 0; i < s.length(); i++) {
			if (s.charAt(i) != t.charAt(i)) {
				count++;
			}
		}
		System.out.println(count);
	}
} import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		String s = scan.nextLine();
		String t = scan.nextLine();
		scan.close();
		int count = 0;
		for (int i = 0; i < s.length(); i++) {
			if (s.charAt(i) != t.charAt(i)) {
				count++;
			}
		}
		System.out.println(count);
	}
} Main public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		String s = scan.nextLine();
		String t = scan.nextLine();
		scan.close();
		int count = 0;
		for (int i = 0; i < s.length(); i++) {
			if (s.charAt(i) != t.charAt(i)) {
				count++;
			}
		}
		System.out.println(count);
	} main {
		Scanner scan = new Scanner(System.in);
		String s = scan.nextLine();
		String t = scan.nextLine();
		scan.close();
		int count = 0;
		for (int i = 0; i < s.length(); i++) {
			if (s.charAt(i) != t.charAt(i)) {
				count++;
			}
		}
		System.out.println(count);
	} Scanner scan = new Scanner(System.in); scan new Scanner(System.in) String s = scan.nextLine(); s scan.nextLine() scan.nextLine scan String t = scan.nextLine(); t scan.nextLine() scan.nextLine scan scan.close() scan.close scan int count = 0; count 0 for (int i = 0; i < s.length(); i++) {
			if (s.charAt(i) != t.charAt(i)) {
				count++;
			}
		} 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)) {
				count++;
			}
		} {
			if (s.charAt(i) != t.charAt(i)) {
				count++;
			}
		} if (s.charAt(i) != t.charAt(i)) {
				count++;
			} s.charAt(i) != t.charAt(i) s.charAt(i) s.charAt s i t.charAt(i) t.charAt 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) {
		Scanner scan = new Scanner(System.in);
		String s = scan.nextLine();
		String t = scan.nextLine();
		scan.close();
		int count = 0;
		for (int i = 0; i < s.length(); i++) {
			if (s.charAt(i) != t.charAt(i)) {
				count++;
			}
		}
		System.out.println(count);
	}
} public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		String s = scan.nextLine();
		String t = scan.nextLine();
		scan.close();
		int count = 0;
		for (int i = 0; i < s.length(); i++) {
			if (s.charAt(i) != t.charAt(i)) {
				count++;
			}
		}
		System.out.println(count);
	}
} Main
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		String s = scan.nextLine();
		String t = scan.nextLine();
		scan.close();
		int count = 0;
		for (int i = 0; i < s.length(); i++) {
			if (s.charAt(i) != t.charAt(i)) {
				count++;
			}
		}
		System.out.println(count);
	}
}