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