import java.util.Scanner;

public class Main {
	
	
	public static void main(String[] args) throws Exception{
		Scanner sc= new Scanner(System.in);
		String n= sc.nextLine();
		
		String n2= sc.nextLine();
		int count=0;
		for(int i=0; i<n.length(); i++) {
			if(n.charAt(i)!=n2.charAt(i))
			count++;
		}
		
		System.out.println(count);
	}
} import java.util.Scanner; Scanner java.util public class Main {
	
	
	public static void main(String[] args) throws Exception{
		Scanner sc= new Scanner(System.in);
		String n= sc.nextLine();
		
		String n2= sc.nextLine();
		int count=0;
		for(int i=0; i<n.length(); i++) {
			if(n.charAt(i)!=n2.charAt(i))
			count++;
		}
		
		System.out.println(count);
	}
} Main public static void main(String[] args) throws Exception{
		Scanner sc= new Scanner(System.in);
		String n= sc.nextLine();
		
		String n2= sc.nextLine();
		int count=0;
		for(int i=0; i<n.length(); i++) {
			if(n.charAt(i)!=n2.charAt(i))
			count++;
		}
		
		System.out.println(count);
	} main {
		Scanner sc= new Scanner(System.in);
		String n= sc.nextLine();
		
		String n2= sc.nextLine();
		int count=0;
		for(int i=0; i<n.length(); i++) {
			if(n.charAt(i)!=n2.charAt(i))
			count++;
		}
		
		System.out.println(count);
	} Scanner sc= new Scanner(System.in); sc new Scanner(System.in) String n= sc.nextLine(); n sc.nextLine() sc.nextLine sc String n2= sc.nextLine(); n2 sc.nextLine() sc.nextLine sc int count=0; count 0 for(int i=0; i<n.length(); i++) {
			if(n.charAt(i)!=n2.charAt(i))
			count++;
		} int i=0; int i=0; i 0 i<n.length() i n.length() n.length n i++ i++ i {
			if(n.charAt(i)!=n2.charAt(i))
			count++;
		} {
			if(n.charAt(i)!=n2.charAt(i))
			count++;
		} if(n.charAt(i)!=n2.charAt(i))
			count++; n.charAt(i)!=n2.charAt(i) n.charAt(i) n.charAt n i n2.charAt(i) n2.charAt n2 i 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) throws Exception{
		Scanner sc= new Scanner(System.in);
		String n= sc.nextLine();
		
		String n2= sc.nextLine();
		int count=0;
		for(int i=0; i<n.length(); i++) {
			if(n.charAt(i)!=n2.charAt(i))
			count++;
		}
		
		System.out.println(count);
	}
} public class Main {
	
	
	public static void main(String[] args) throws Exception{
		Scanner sc= new Scanner(System.in);
		String n= sc.nextLine();
		
		String n2= sc.nextLine();
		int count=0;
		for(int i=0; i<n.length(); i++) {
			if(n.charAt(i)!=n2.charAt(i))
			count++;
		}
		
		System.out.println(count);
	}
} Main
import java.util.Scanner;

public class Main {
	
	
	public static void main(String[] args) throws Exception{
		Scanner sc= new Scanner(System.in);
		String n= sc.nextLine();
		
		String n2= sc.nextLine();
		int count=0;
		for(int i=0; i<n.length(); i++) {
			if(n.charAt(i)!=n2.charAt(i))
			count++;
		}
		
		System.out.println(count);
	}
}
