
import java.util.*;
import java.math.*;
public class Main {
	public static void main(String[] args){
		
		Scanner sc = new Scanner(System.in);
		String S = sc.next();
		String T = sc.next();
		int A = 0;
		
		char[] s2 = S.toCharArray();
		char[] t2 = T.toCharArray();
		
		for (int i = 0 ; i < s2.length; i++)
		{
			if (s2[i]!=t2[i])
			{A++;}
			
		}
		
		
		System.out.println(A);
   
        }
		
	} import java.util.*; util.* java import java.math.*; math.* java public class Main {
	public static void main(String[] args){
		
		Scanner sc = new Scanner(System.in);
		String S = sc.next();
		String T = sc.next();
		int A = 0;
		
		char[] s2 = S.toCharArray();
		char[] t2 = T.toCharArray();
		
		for (int i = 0 ; i < s2.length; i++)
		{
			if (s2[i]!=t2[i])
			{A++;}
			
		}
		
		
		System.out.println(A);
   
        }
		
	} Main public static void main(String[] args){
		
		Scanner sc = new Scanner(System.in);
		String S = sc.next();
		String T = sc.next();
		int A = 0;
		
		char[] s2 = S.toCharArray();
		char[] t2 = T.toCharArray();
		
		for (int i = 0 ; i < s2.length; i++)
		{
			if (s2[i]!=t2[i])
			{A++;}
			
		}
		
		
		System.out.println(A);
   
        } main {
		
		Scanner sc = new Scanner(System.in);
		String S = sc.next();
		String T = sc.next();
		int A = 0;
		
		char[] s2 = S.toCharArray();
		char[] t2 = T.toCharArray();
		
		for (int i = 0 ; i < s2.length; i++)
		{
			if (s2[i]!=t2[i])
			{A++;}
			
		}
		
		
		System.out.println(A);
   
        } 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 A = 0; A 0 char[] s2 = S.toCharArray(); s2 S.toCharArray() S.toCharArray S char[] t2 = T.toCharArray(); t2 T.toCharArray() T.toCharArray T for (int i = 0 ; i < s2.length; i++)
		{
			if (s2[i]!=t2[i])
			{A++;}
			
		} int i = 0 ; int i = 0 ; i 0 i < s2.length i s2.length s2 s2.length i++ i++ i {
			if (s2[i]!=t2[i])
			{A++;}
			
		} {
			if (s2[i]!=t2[i])
			{A++;}
			
		} if (s2[i]!=t2[i])
			{A++;} s2[i]!=t2[i] s2[i] s2 i t2[i] t2 i {A++;} A++ A System.out.println(A) System.out.println System.out System System.out A 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 A = 0;
		
		char[] s2 = S.toCharArray();
		char[] t2 = T.toCharArray();
		
		for (int i = 0 ; i < s2.length; i++)
		{
			if (s2[i]!=t2[i])
			{A++;}
			
		}
		
		
		System.out.println(A);
   
        }
		
	} public class Main {
	public static void main(String[] args){
		
		Scanner sc = new Scanner(System.in);
		String S = sc.next();
		String T = sc.next();
		int A = 0;
		
		char[] s2 = S.toCharArray();
		char[] t2 = T.toCharArray();
		
		for (int i = 0 ; i < s2.length; i++)
		{
			if (s2[i]!=t2[i])
			{A++;}
			
		}
		
		
		System.out.println(A);
   
        }
		
	} Main

import java.util.*;
import java.math.*;
public class Main {
	public static void main(String[] args){
		
		Scanner sc = new Scanner(System.in);
		String S = sc.next();
		String T = sc.next();
		int A = 0;
		
		char[] s2 = S.toCharArray();
		char[] t2 = T.toCharArray();
		
		for (int i = 0 ; i < s2.length; i++)
		{
			if (s2[i]!=t2[i])
			{A++;}
			
		}
		
		
		System.out.println(A);
   
        }
		
	}