import java.util.Scanner;

public class Main{
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		String str1 = scan.next();
		String str2 = scan.next();
		int cnt = 0;

		for(int i = -1+str1.length();i>=0;i--) {
			if(str1.charAt(i) != str2.charAt(i)) {
				cnt += 1;
			}
		}
		System.out.println(cnt);

		scan.close();
	}
} import java.util.Scanner; Scanner java.util public class Main{
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		String str1 = scan.next();
		String str2 = scan.next();
		int cnt = 0;

		for(int i = -1+str1.length();i>=0;i--) {
			if(str1.charAt(i) != str2.charAt(i)) {
				cnt += 1;
			}
		}
		System.out.println(cnt);

		scan.close();
	}
} Main public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		String str1 = scan.next();
		String str2 = scan.next();
		int cnt = 0;

		for(int i = -1+str1.length();i>=0;i--) {
			if(str1.charAt(i) != str2.charAt(i)) {
				cnt += 1;
			}
		}
		System.out.println(cnt);

		scan.close();
	} main {
		Scanner scan = new Scanner(System.in);
		String str1 = scan.next();
		String str2 = scan.next();
		int cnt = 0;

		for(int i = -1+str1.length();i>=0;i--) {
			if(str1.charAt(i) != str2.charAt(i)) {
				cnt += 1;
			}
		}
		System.out.println(cnt);

		scan.close();
	} Scanner scan = new Scanner(System.in); scan new Scanner(System.in) String str1 = scan.next(); str1 scan.next() scan.next scan String str2 = scan.next(); str2 scan.next() scan.next scan int cnt = 0; cnt 0 for(int i = -1+str1.length();i>=0;i--) {
			if(str1.charAt(i) != str2.charAt(i)) {
				cnt += 1;
			}
		} int i = -1+str1.length(); int i = -1+str1.length(); i -1+str1.length() -1 1 str1.length() str1.length str1 i>=0 i 0 i-- i-- i {
			if(str1.charAt(i) != str2.charAt(i)) {
				cnt += 1;
			}
		} {
			if(str1.charAt(i) != str2.charAt(i)) {
				cnt += 1;
			}
		} if(str1.charAt(i) != str2.charAt(i)) {
				cnt += 1;
			} str1.charAt(i) != str2.charAt(i) str1.charAt(i) str1.charAt str1 i str2.charAt(i) str2.charAt str2 i {
				cnt += 1;
			} cnt += 1 cnt 1 System.out.println(cnt) System.out.println System.out System System.out cnt scan.close() scan.close scan String[] args args public class Main{
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		String str1 = scan.next();
		String str2 = scan.next();
		int cnt = 0;

		for(int i = -1+str1.length();i>=0;i--) {
			if(str1.charAt(i) != str2.charAt(i)) {
				cnt += 1;
			}
		}
		System.out.println(cnt);

		scan.close();
	}
} public class Main{
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		String str1 = scan.next();
		String str2 = scan.next();
		int cnt = 0;

		for(int i = -1+str1.length();i>=0;i--) {
			if(str1.charAt(i) != str2.charAt(i)) {
				cnt += 1;
			}
		}
		System.out.println(cnt);

		scan.close();
	}
} Main
import java.util.Scanner;

public class Main{
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		String str1 = scan.next();
		String str2 = scan.next();
		int cnt = 0;

		for(int i = -1+str1.length();i>=0;i--) {
			if(str1.charAt(i) != str2.charAt(i)) {
				cnt += 1;
			}
		}
		System.out.println(cnt);

		scan.close();
	}
}