
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String[] line_S = sc.nextLine().split("", 0);
		String[] line_T = sc.nextLine().split("", 0);
		int con = 0;
		for (int i = 0; i < line_S.length; i++) {
			if (line_S[i].compareTo(line_T[i]) != 0) {
				con++;
			}
		}
		System.out.println(con);
	}
} import java.util.Scanner; Scanner java.util public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String[] line_S = sc.nextLine().split("", 0);
		String[] line_T = sc.nextLine().split("", 0);
		int con = 0;
		for (int i = 0; i < line_S.length; i++) {
			if (line_S[i].compareTo(line_T[i]) != 0) {
				con++;
			}
		}
		System.out.println(con);
	}
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String[] line_S = sc.nextLine().split("", 0);
		String[] line_T = sc.nextLine().split("", 0);
		int con = 0;
		for (int i = 0; i < line_S.length; i++) {
			if (line_S[i].compareTo(line_T[i]) != 0) {
				con++;
			}
		}
		System.out.println(con);
	} main {
		Scanner sc = new Scanner(System.in);
		String[] line_S = sc.nextLine().split("", 0);
		String[] line_T = sc.nextLine().split("", 0);
		int con = 0;
		for (int i = 0; i < line_S.length; i++) {
			if (line_S[i].compareTo(line_T[i]) != 0) {
				con++;
			}
		}
		System.out.println(con);
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) String[] line_S = sc.nextLine().split("", 0); line_S sc.nextLine().split("", 0) sc.nextLine().split sc.nextLine() sc.nextLine sc "" 0 String[] line_T = sc.nextLine().split("", 0); line_T sc.nextLine().split("", 0) sc.nextLine().split sc.nextLine() sc.nextLine sc "" 0 int con = 0; con 0 for (int i = 0; i < line_S.length; i++) {
			if (line_S[i].compareTo(line_T[i]) != 0) {
				con++;
			}
		} int i = 0; int i = 0; i 0 i < line_S.length i line_S.length line_S line_S.length i++ i++ i {
			if (line_S[i].compareTo(line_T[i]) != 0) {
				con++;
			}
		} {
			if (line_S[i].compareTo(line_T[i]) != 0) {
				con++;
			}
		} if (line_S[i].compareTo(line_T[i]) != 0) {
				con++;
			} line_S[i].compareTo(line_T[i]) != 0 line_S[i].compareTo(line_T[i]) line_S[i].compareTo line_S[i] line_S i line_T[i] line_T i 0 {
				con++;
			} con++ con System.out.println(con) System.out.println System.out System System.out con String[] args args public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String[] line_S = sc.nextLine().split("", 0);
		String[] line_T = sc.nextLine().split("", 0);
		int con = 0;
		for (int i = 0; i < line_S.length; i++) {
			if (line_S[i].compareTo(line_T[i]) != 0) {
				con++;
			}
		}
		System.out.println(con);
	}
} public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String[] line_S = sc.nextLine().split("", 0);
		String[] line_T = sc.nextLine().split("", 0);
		int con = 0;
		for (int i = 0; i < line_S.length; i++) {
			if (line_S[i].compareTo(line_T[i]) != 0) {
				con++;
			}
		}
		System.out.println(con);
	}
} Main

import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String[] line_S = sc.nextLine().split("", 0);
		String[] line_T = sc.nextLine().split("", 0);
		int con = 0;
		for (int i = 0; i < line_S.length; i++) {
			if (line_S[i].compareTo(line_T[i]) != 0) {
				con++;
			}
		}
		System.out.println(con);
	}
}
