import java.util.Scanner;

public class Main{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String str = sc.next();
		String str2 = sc.next();
		
		Integer count = 0;
		
		for(int i = 0; i < str.length(); i++) {
			if(str.charAt(i) != str2.charAt(i)) {
				count ++ ;
			}
		}
		System.out.println(count);
	}
} import java.util.Scanner; Scanner java.util public class Main{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String str = sc.next();
		String str2 = sc.next();
		
		Integer count = 0;
		
		for(int i = 0; i < str.length(); i++) {
			if(str.charAt(i) != str2.charAt(i)) {
				count ++ ;
			}
		}
		System.out.println(count);
	}
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String str = sc.next();
		String str2 = sc.next();
		
		Integer count = 0;
		
		for(int i = 0; i < str.length(); i++) {
			if(str.charAt(i) != str2.charAt(i)) {
				count ++ ;
			}
		}
		System.out.println(count);
	} main {
		Scanner sc = new Scanner(System.in);
		String str = sc.next();
		String str2 = sc.next();
		
		Integer count = 0;
		
		for(int i = 0; i < str.length(); i++) {
			if(str.charAt(i) != str2.charAt(i)) {
				count ++ ;
			}
		}
		System.out.println(count);
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) String str = sc.next(); str sc.next() sc.next sc String str2 = sc.next(); str2 sc.next() sc.next sc Integer count = 0; count 0 for(int i = 0; i < str.length(); i++) {
			if(str.charAt(i) != str2.charAt(i)) {
				count ++ ;
			}
		} int i = 0; int i = 0; i 0 i < str.length() i str.length() str.length str i++ i++ i {
			if(str.charAt(i) != str2.charAt(i)) {
				count ++ ;
			}
		} {
			if(str.charAt(i) != str2.charAt(i)) {
				count ++ ;
			}
		} if(str.charAt(i) != str2.charAt(i)) {
				count ++ ;
			} str.charAt(i) != str2.charAt(i) str.charAt(i) str.charAt str i str2.charAt(i) str2.charAt str2 i {
				count ++ ;
			} count ++ count System.out.println(count) System.out.println System.out System System.out count String[] args args public class Main{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String str = sc.next();
		String str2 = sc.next();
		
		Integer count = 0;
		
		for(int i = 0; i < str.length(); i++) {
			if(str.charAt(i) != str2.charAt(i)) {
				count ++ ;
			}
		}
		System.out.println(count);
	}
} public class Main{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String str = sc.next();
		String str2 = sc.next();
		
		Integer count = 0;
		
		for(int i = 0; i < str.length(); i++) {
			if(str.charAt(i) != str2.charAt(i)) {
				count ++ ;
			}
		}
		System.out.println(count);
	}
} Main
import java.util.Scanner;

public class Main{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String str = sc.next();
		String str2 = sc.next();
		
		Integer count = 0;
		
		for(int i = 0; i < str.length(); i++) {
			if(str.charAt(i) != str2.charAt(i)) {
				count ++ ;
			}
		}
		System.out.println(count);
	}
}
