/* package codechef; // don't place package name! */

import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
class Main
{
	public static void main (String[] args) throws java.lang.Exception
	{
	    Scanner sc=new Scanner(System.in);
	    String t=sc.nextLine();
	    String s=sc.nextLine();
	    int x=t.length();
	    int c=0;
	    for(int i=0;i<x;i++)
	    {
	        if(t.charAt(i)!=s.charAt(i))
	        c++;
	       }
	       System.out.println(c);
	   }
} import java.util.*; util.* java import java.lang.*; lang.* java import java.io.*; io.* java class Main
{
	public static void main (String[] args) throws java.lang.Exception
	{
	    Scanner sc=new Scanner(System.in);
	    String t=sc.nextLine();
	    String s=sc.nextLine();
	    int x=t.length();
	    int c=0;
	    for(int i=0;i<x;i++)
	    {
	        if(t.charAt(i)!=s.charAt(i))
	        c++;
	       }
	       System.out.println(c);
	   }
} Main public static void main (String[] args) throws java.lang.Exception
	{
	    Scanner sc=new Scanner(System.in);
	    String t=sc.nextLine();
	    String s=sc.nextLine();
	    int x=t.length();
	    int c=0;
	    for(int i=0;i<x;i++)
	    {
	        if(t.charAt(i)!=s.charAt(i))
	        c++;
	       }
	       System.out.println(c);
	   } main {
	    Scanner sc=new Scanner(System.in);
	    String t=sc.nextLine();
	    String s=sc.nextLine();
	    int x=t.length();
	    int c=0;
	    for(int i=0;i<x;i++)
	    {
	        if(t.charAt(i)!=s.charAt(i))
	        c++;
	       }
	       System.out.println(c);
	   } Scanner sc=new Scanner(System.in); sc new Scanner(System.in) String t=sc.nextLine(); t sc.nextLine() sc.nextLine sc String s=sc.nextLine(); s sc.nextLine() sc.nextLine sc int x=t.length(); x t.length() t.length t int c=0; c 0 for(int i=0;i<x;i++)
	    {
	        if(t.charAt(i)!=s.charAt(i))
	        c++;
	       } int i=0; int i=0; i 0 i<x i x i++ i++ i {
	        if(t.charAt(i)!=s.charAt(i))
	        c++;
	       } {
	        if(t.charAt(i)!=s.charAt(i))
	        c++;
	       } if(t.charAt(i)!=s.charAt(i))
	        c++; t.charAt(i)!=s.charAt(i) t.charAt(i) t.charAt t i s.charAt(i) s.charAt s i c++ c System.out.println(c) System.out.println System.out System System.out c String[] args args
/* package codechef; // don't place package name! */

import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
class Main
{
	public static void main (String[] args) throws java.lang.Exception
	{
	    Scanner sc=new Scanner(System.in);
	    String t=sc.nextLine();
	    String s=sc.nextLine();
	    int x=t.length();
	    int c=0;
	    for(int i=0;i<x;i++)
	    {
	        if(t.charAt(i)!=s.charAt(i))
	        c++;
	       }
	       System.out.println(c);
	   }
}