import java.util.Scanner;

public class Main{

	public static void main(String[] args) {

		Scanner scanner = new Scanner(System.in);
		char[] s = scanner.nextLine().toCharArray();
		char[] t = scanner.nextLine().toCharArray();
		long ans = 0;

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

			if(s[i] != t[i]) ans++;

		}

 		System.out.println(ans);
	}
} import java.util.Scanner; Scanner java.util public class Main{

	public static void main(String[] args) {

		Scanner scanner = new Scanner(System.in);
		char[] s = scanner.nextLine().toCharArray();
		char[] t = scanner.nextLine().toCharArray();
		long ans = 0;

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

			if(s[i] != t[i]) ans++;

		}

 		System.out.println(ans);
	}
} Main public static void main(String[] args) {

		Scanner scanner = new Scanner(System.in);
		char[] s = scanner.nextLine().toCharArray();
		char[] t = scanner.nextLine().toCharArray();
		long ans = 0;

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

			if(s[i] != t[i]) ans++;

		}

 		System.out.println(ans);
	} main {

		Scanner scanner = new Scanner(System.in);
		char[] s = scanner.nextLine().toCharArray();
		char[] t = scanner.nextLine().toCharArray();
		long ans = 0;

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

			if(s[i] != t[i]) ans++;

		}

 		System.out.println(ans);
	} Scanner scanner = new Scanner(System.in); scanner new Scanner(System.in) char[] s = scanner.nextLine().toCharArray(); s scanner.nextLine().toCharArray() scanner.nextLine().toCharArray scanner.nextLine() scanner.nextLine scanner char[] t = scanner.nextLine().toCharArray(); t scanner.nextLine().toCharArray() scanner.nextLine().toCharArray scanner.nextLine() scanner.nextLine scanner long ans = 0; ans 0 for(int i = 0; i < s.length; i++) {

			if(s[i] != t[i]) ans++;

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

			if(s[i] != t[i]) ans++;

		} {

			if(s[i] != t[i]) ans++;

		} if(s[i] != t[i]) ans++; s[i] != t[i] s[i] s i t[i] t i ans++ ans System.out.println(ans) System.out.println System.out System System.out ans String[] args args public class Main{

	public static void main(String[] args) {

		Scanner scanner = new Scanner(System.in);
		char[] s = scanner.nextLine().toCharArray();
		char[] t = scanner.nextLine().toCharArray();
		long ans = 0;

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

			if(s[i] != t[i]) ans++;

		}

 		System.out.println(ans);
	}
} public class Main{

	public static void main(String[] args) {

		Scanner scanner = new Scanner(System.in);
		char[] s = scanner.nextLine().toCharArray();
		char[] t = scanner.nextLine().toCharArray();
		long ans = 0;

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

			if(s[i] != t[i]) ans++;

		}

 		System.out.println(ans);
	}
} Main
import java.util.Scanner;

public class Main{

	public static void main(String[] args) {

		Scanner scanner = new Scanner(System.in);
		char[] s = scanner.nextLine().toCharArray();
		char[] t = scanner.nextLine().toCharArray();
		long ans = 0;

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

			if(s[i] != t[i]) ans++;

		}

 		System.out.println(ans);
	}
}
