
import java.util.*;

public class Main {

	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);
		String s = sc.next();
		String t = sc.next();

		int n = s.length();
		int result = 0;

		for (int i = 0; i <= n - 1; i++) {
			String a = s.substring(i, i + 1);
			String b = t.substring(i, i + 1);
			//System.out.println(a);
			//System.out.println(b);

			if (a.equals(b)) {
				//System.out.println("OK " + result);
			} else {
				result++;
				//System.out.println("NG " + result);
			}
		}

		System.out.println(result);

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

	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);
		String s = sc.next();
		String t = sc.next();

		int n = s.length();
		int result = 0;

		for (int i = 0; i <= n - 1; i++) {
			String a = s.substring(i, i + 1);
			String b = t.substring(i, i + 1);
			//System.out.println(a);
			//System.out.println(b);

			if (a.equals(b)) {
				//System.out.println("OK " + result);
			} else {
				result++;
				//System.out.println("NG " + result);
			}
		}

		System.out.println(result);

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

		Scanner sc = new Scanner(System.in);
		String s = sc.next();
		String t = sc.next();

		int n = s.length();
		int result = 0;

		for (int i = 0; i <= n - 1; i++) {
			String a = s.substring(i, i + 1);
			String b = t.substring(i, i + 1);
			//System.out.println(a);
			//System.out.println(b);

			if (a.equals(b)) {
				//System.out.println("OK " + result);
			} else {
				result++;
				//System.out.println("NG " + result);
			}
		}

		System.out.println(result);

	} main {

		Scanner sc = new Scanner(System.in);
		String s = sc.next();
		String t = sc.next();

		int n = s.length();
		int result = 0;

		for (int i = 0; i <= n - 1; i++) {
			String a = s.substring(i, i + 1);
			String b = t.substring(i, i + 1);
			//System.out.println(a);
			//System.out.println(b);

			if (a.equals(b)) {
				//System.out.println("OK " + result);
			} else {
				result++;
				//System.out.println("NG " + result);
			}
		}

		System.out.println(result);

	} Scanner sc = new Scanner(System.in); sc 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 n = s.length(); n s.length() s.length s int result = 0; result 0 for (int i = 0; i <= n - 1; i++) {
			String a = s.substring(i, i + 1);
			String b = t.substring(i, i + 1);
			//System.out.println(a);
			//System.out.println(b);

			if (a.equals(b)) {
				//System.out.println("OK " + result);
			} else {
				result++;
				//System.out.println("NG " + result);
			}
		} int i = 0; int i = 0; i 0 i <= n - 1 i n - 1 n 1 i++ i++ i {
			String a = s.substring(i, i + 1);
			String b = t.substring(i, i + 1);
			//System.out.println(a);
			//System.out.println(b);

			if (a.equals(b)) {
				//System.out.println("OK " + result);
			} else {
				result++;
				//System.out.println("NG " + result);
			}
		} {
			String a = s.substring(i, i + 1);
			String b = t.substring(i, i + 1);
			//System.out.println(a);
			//System.out.println(b);

			if (a.equals(b)) {
				//System.out.println("OK " + result);
			} else {
				result++;
				//System.out.println("NG " + result);
			}
		} String a = s.substring(i, i + 1); a s.substring(i, i + 1) s.substring s i i + 1 i 1 String b = t.substring(i, i + 1); b t.substring(i, i + 1) t.substring t i i + 1 i 1 if (a.equals(b)) {
				//System.out.println("OK " + result);
			} else {
				result++;
				//System.out.println("NG " + result);
			} a.equals(b) a.equals a b {
				//System.out.println("OK " + result);
			} {
				result++;
				//System.out.println("NG " + result);
			} result++ result System.out.println(result) System.out.println System.out System System.out result String[] args args public class Main {

	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);
		String s = sc.next();
		String t = sc.next();

		int n = s.length();
		int result = 0;

		for (int i = 0; i <= n - 1; i++) {
			String a = s.substring(i, i + 1);
			String b = t.substring(i, i + 1);
			//System.out.println(a);
			//System.out.println(b);

			if (a.equals(b)) {
				//System.out.println("OK " + result);
			} else {
				result++;
				//System.out.println("NG " + result);
			}
		}

		System.out.println(result);

	}
} public class Main {

	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);
		String s = sc.next();
		String t = sc.next();

		int n = s.length();
		int result = 0;

		for (int i = 0; i <= n - 1; i++) {
			String a = s.substring(i, i + 1);
			String b = t.substring(i, i + 1);
			//System.out.println(a);
			//System.out.println(b);

			if (a.equals(b)) {
				//System.out.println("OK " + result);
			} else {
				result++;
				//System.out.println("NG " + result);
			}
		}

		System.out.println(result);

	}
} Main

import java.util.*;

public class Main {

	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);
		String s = sc.next();
		String t = sc.next();

		int n = s.length();
		int result = 0;

		for (int i = 0; i <= n - 1; i++) {
			String a = s.substring(i, i + 1);
			String b = t.substring(i, i + 1);
			//System.out.println(a);
			//System.out.println(b);

			if (a.equals(b)) {
				//System.out.println("OK " + result);
			} else {
				result++;
				//System.out.println("NG " + result);
			}
		}

		System.out.println(result);

	}
}