import java.util.*;
public class Main{
  public static void main(String[] args)
  {
    Scanner sc=new Scanner(System.in);
   String s1=sc.next();
   String s2=sc.next();
  int c=0;
  if(!(s1.equals(s2)))
  {
   for(int i=0;i<s1.length();i++) 
  {
       if(s1.charAt(i)!=s2.charAt(i))
	c++;
   }
  }
   System.out.println(c); 
  }
   
} import java.util.*; util.* java public class Main{
  public static void main(String[] args)
  {
    Scanner sc=new Scanner(System.in);
   String s1=sc.next();
   String s2=sc.next();
  int c=0;
  if(!(s1.equals(s2)))
  {
   for(int i=0;i<s1.length();i++) 
  {
       if(s1.charAt(i)!=s2.charAt(i))
	c++;
   }
  }
   System.out.println(c); 
  }
   
} Main public static void main(String[] args)
  {
    Scanner sc=new Scanner(System.in);
   String s1=sc.next();
   String s2=sc.next();
  int c=0;
  if(!(s1.equals(s2)))
  {
   for(int i=0;i<s1.length();i++) 
  {
       if(s1.charAt(i)!=s2.charAt(i))
	c++;
   }
  }
   System.out.println(c); 
  } main {
    Scanner sc=new Scanner(System.in);
   String s1=sc.next();
   String s2=sc.next();
  int c=0;
  if(!(s1.equals(s2)))
  {
   for(int i=0;i<s1.length();i++) 
  {
       if(s1.charAt(i)!=s2.charAt(i))
	c++;
   }
  }
   System.out.println(c); 
  } Scanner sc=new Scanner(System.in); sc new Scanner(System.in) String s1=sc.next(); s1 sc.next() sc.next sc String s2=sc.next(); s2 sc.next() sc.next sc int c=0; c 0 if(!(s1.equals(s2)))
  {
   for(int i=0;i<s1.length();i++) 
  {
       if(s1.charAt(i)!=s2.charAt(i))
	c++;
   }
  } !(s1.equals(s2)) (s1.equals(s2)) s1.equals s1 s2 {
   for(int i=0;i<s1.length();i++) 
  {
       if(s1.charAt(i)!=s2.charAt(i))
	c++;
   }
  } for(int i=0;i<s1.length();i++) 
  {
       if(s1.charAt(i)!=s2.charAt(i))
	c++;
   } int i=0; int i=0; i 0 i<s1.length() i s1.length() s1.length s1 i++ i++ i {
       if(s1.charAt(i)!=s2.charAt(i))
	c++;
   } {
       if(s1.charAt(i)!=s2.charAt(i))
	c++;
   } if(s1.charAt(i)!=s2.charAt(i))
	c++; s1.charAt(i)!=s2.charAt(i) s1.charAt(i) s1.charAt s1 i s2.charAt(i) s2.charAt s2 i c++ c System.out.println(c) System.out.println System.out System System.out c String[] args args public class Main{
  public static void main(String[] args)
  {
    Scanner sc=new Scanner(System.in);
   String s1=sc.next();
   String s2=sc.next();
  int c=0;
  if(!(s1.equals(s2)))
  {
   for(int i=0;i<s1.length();i++) 
  {
       if(s1.charAt(i)!=s2.charAt(i))
	c++;
   }
  }
   System.out.println(c); 
  }
   
} public class Main{
  public static void main(String[] args)
  {
    Scanner sc=new Scanner(System.in);
   String s1=sc.next();
   String s2=sc.next();
  int c=0;
  if(!(s1.equals(s2)))
  {
   for(int i=0;i<s1.length();i++) 
  {
       if(s1.charAt(i)!=s2.charAt(i))
	c++;
   }
  }
   System.out.println(c); 
  }
   
} Main
import java.util.*;
public class Main{
  public static void main(String[] args)
  {
    Scanner sc=new Scanner(System.in);
   String s1=sc.next();
   String s2=sc.next();
  int c=0;
  if(!(s1.equals(s2)))
  {
   for(int i=0;i<s1.length();i++) 
  {
       if(s1.charAt(i)!=s2.charAt(i))
	c++;
   }
  }
   System.out.println(c); 
  }
   
}