import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		try(Scanner sc = new Scanner(System.in)){
			String s = sc.next();
			String t = sc.next();

			int cnt = 0;

			for(int it = 0; it < s.length(); it++) {
				if(s.charAt(it) != t.charAt(it)) {
					cnt++;
				}
			}
			System.out.println(cnt);
		}
	}
} import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args) {
		try(Scanner sc = new Scanner(System.in)){
			String s = sc.next();
			String t = sc.next();

			int cnt = 0;

			for(int it = 0; it < s.length(); it++) {
				if(s.charAt(it) != t.charAt(it)) {
					cnt++;
				}
			}
			System.out.println(cnt);
		}
	}
} Main public static void main(String[] args) {
		try(Scanner sc = new Scanner(System.in)){
			String s = sc.next();
			String t = sc.next();

			int cnt = 0;

			for(int it = 0; it < s.length(); it++) {
				if(s.charAt(it) != t.charAt(it)) {
					cnt++;
				}
			}
			System.out.println(cnt);
		}
	} main {
		try(Scanner sc = new Scanner(System.in)){
			String s = sc.next();
			String t = sc.next();

			int cnt = 0;

			for(int it = 0; it < s.length(); it++) {
				if(s.charAt(it) != t.charAt(it)) {
					cnt++;
				}
			}
			System.out.println(cnt);
		}
	} try(Scanner sc = new Scanner(System.in)){
			String s = sc.next();
			String t = sc.next();

			int cnt = 0;

			for(int it = 0; it < s.length(); it++) {
				if(s.charAt(it) != t.charAt(it)) {
					cnt++;
				}
			}
			System.out.println(cnt);
		} {
			String s = sc.next();
			String t = sc.next();

			int cnt = 0;

			for(int it = 0; it < s.length(); it++) {
				if(s.charAt(it) != t.charAt(it)) {
					cnt++;
				}
			}
			System.out.println(cnt);
		} Scanner sc = new Scanner(System.in) Scanner sc = new Scanner(System.in) new Scanner(System.in) String s = sc.next(); s sc.next() sc.next sc String t = sc.next(); t sc.next() sc.next sc int cnt = 0; cnt 0 for(int it = 0; it < s.length(); it++) {
				if(s.charAt(it) != t.charAt(it)) {
					cnt++;
				}
			} int it = 0; int it = 0; it 0 it < s.length() it s.length() s.length s it++ it++ it {
				if(s.charAt(it) != t.charAt(it)) {
					cnt++;
				}
			} {
				if(s.charAt(it) != t.charAt(it)) {
					cnt++;
				}
			} if(s.charAt(it) != t.charAt(it)) {
					cnt++;
				} s.charAt(it) != t.charAt(it) s.charAt(it) s.charAt s it t.charAt(it) t.charAt t it {
					cnt++;
				} cnt++ cnt System.out.println(cnt) System.out.println System.out System System.out cnt String[] args args public class Main {
	public static void main(String[] args) {
		try(Scanner sc = new Scanner(System.in)){
			String s = sc.next();
			String t = sc.next();

			int cnt = 0;

			for(int it = 0; it < s.length(); it++) {
				if(s.charAt(it) != t.charAt(it)) {
					cnt++;
				}
			}
			System.out.println(cnt);
		}
	}
} public class Main {
	public static void main(String[] args) {
		try(Scanner sc = new Scanner(System.in)){
			String s = sc.next();
			String t = sc.next();

			int cnt = 0;

			for(int it = 0; it < s.length(); it++) {
				if(s.charAt(it) != t.charAt(it)) {
					cnt++;
				}
			}
			System.out.println(cnt);
		}
	}
} Main
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		try(Scanner sc = new Scanner(System.in)){
			String s = sc.next();
			String t = sc.next();

			int cnt = 0;

			for(int it = 0; it < s.length(); it++) {
				if(s.charAt(it) != t.charAt(it)) {
					cnt++;
				}
			}
			System.out.println(cnt);
		}
	}
}
