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



/* Name of the class has to be "Main" only if the class is public. */



public class Main
{
     
     
     static int mod(int a, int m) 
{ 
    return (a%m + m) % m; 
}
   
    
public static void main (String[] args) throws java.lang.Exception
{Scanner scn = new Scanner(System.in) ;

String s  = scn.nextLine() ;
String t  = scn.nextLine() ; int count  = 0 ;

for(int i = 0 ; i <  s.length() ; i++ )
{
    if(s.charAt(i) != t.charAt(i) )count++ ;
    
    
    
}

System.out.println(count) ;
              
}
}




              
              import java.util.*; util.* java import java.lang.*; lang.* java import java.io.*; io.* java public class Main
{
     
     
     static int mod(int a, int m) 
{ 
    return (a%m + m) % m; 
}
   
    
public static void main (String[] args) throws java.lang.Exception
{Scanner scn = new Scanner(System.in) ;

String s  = scn.nextLine() ;
String t  = scn.nextLine() ; int count  = 0 ;

for(int i = 0 ; i <  s.length() ; i++ )
{
    if(s.charAt(i) != t.charAt(i) )count++ ;
    
    
    
}

System.out.println(count) ;
              
}
} Main static int mod(int a, int m) 
{ 
    return (a%m + m) % m; 
} mod { 
    return (a%m + m) % m; 
} return (a%m + m) % m; (a%m + m) % m (a%m + m) a%m a m m m int a a int m m public static void main (String[] args) throws java.lang.Exception
{Scanner scn = new Scanner(System.in) ;

String s  = scn.nextLine() ;
String t  = scn.nextLine() ; int count  = 0 ;

for(int i = 0 ; i <  s.length() ; i++ )
{
    if(s.charAt(i) != t.charAt(i) )count++ ;
    
    
    
}

System.out.println(count) ;
              
} main {Scanner scn = new Scanner(System.in) ;

String s  = scn.nextLine() ;
String t  = scn.nextLine() ; int count  = 0 ;

for(int i = 0 ; i <  s.length() ; i++ )
{
    if(s.charAt(i) != t.charAt(i) )count++ ;
    
    
    
}

System.out.println(count) ;
              
} Scanner scn = new Scanner(System.in) ; scn new Scanner(System.in) String s  = scn.nextLine() ; s scn.nextLine() scn.nextLine scn String t  = scn.nextLine() ; t scn.nextLine() scn.nextLine scn int count  = 0 ; count 0 for(int i = 0 ; i <  s.length() ; i++ )
{
    if(s.charAt(i) != t.charAt(i) )count++ ;
    
    
    
} 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) )count++ ;
    
    
    
} {
    if(s.charAt(i) != t.charAt(i) )count++ ;
    
    
    
} if(s.charAt(i) != t.charAt(i) )count++ ; s.charAt(i) != t.charAt(i) s.charAt(i) s.charAt s i t.charAt(i) t.charAt t i count++ count System.out.println(count) System.out.println System.out System System.out count String[] args args public class Main
{
     
     
     static int mod(int a, int m) 
{ 
    return (a%m + m) % m; 
}
   
    
public static void main (String[] args) throws java.lang.Exception
{Scanner scn = new Scanner(System.in) ;

String s  = scn.nextLine() ;
String t  = scn.nextLine() ; int count  = 0 ;

for(int i = 0 ; i <  s.length() ; i++ )
{
    if(s.charAt(i) != t.charAt(i) )count++ ;
    
    
    
}

System.out.println(count) ;
              
}
} public class Main
{
     
     
     static int mod(int a, int m) 
{ 
    return (a%m + m) % m; 
}
   
    
public static void main (String[] args) throws java.lang.Exception
{Scanner scn = new Scanner(System.in) ;

String s  = scn.nextLine() ;
String t  = scn.nextLine() ; int count  = 0 ;

for(int i = 0 ; i <  s.length() ; i++ )
{
    if(s.charAt(i) != t.charAt(i) )count++ ;
    
    
    
}

System.out.println(count) ;
              
}
} Main
import java.util.*;
import java.lang.*;
import java.io.*;



/* Name of the class has to be "Main" only if the class is public. */



public class Main
{
     
     
     static int mod(int a, int m) 
{ 
    return (a%m + m) % m; 
}
   
    
public static void main (String[] args) throws java.lang.Exception
{Scanner scn = new Scanner(System.in) ;

String s  = scn.nextLine() ;
String t  = scn.nextLine() ; int count  = 0 ;

for(int i = 0 ; i <  s.length() ; i++ )
{
    if(s.charAt(i) != t.charAt(i) )count++ ;
    
    
    
}

System.out.println(count) ;
              
}
}




              
             