import java.util.*;
import java.io.*;
class Main
{
    public static void main(String args[])throws IOException
    {
        Scanner obj=new Scanner(System.in);
        int i,c=0;String ns="";
        String s=obj.nextLine();
        String t=obj.nextLine();
        for(i=0;i<s.length();i++)
           {
               if(s.charAt(i)!=t.charAt(i))
                    c++;
               else
                    continue;
            }
        System.out.println(c);   
    }
} import java.util.*; util.* java import java.io.*; io.* java class Main
{
    public static void main(String args[])throws IOException
    {
        Scanner obj=new Scanner(System.in);
        int i,c=0;String ns="";
        String s=obj.nextLine();
        String t=obj.nextLine();
        for(i=0;i<s.length();i++)
           {
               if(s.charAt(i)!=t.charAt(i))
                    c++;
               else
                    continue;
            }
        System.out.println(c);   
    }
} Main public static void main(String args[])throws IOException
    {
        Scanner obj=new Scanner(System.in);
        int i,c=0;String ns="";
        String s=obj.nextLine();
        String t=obj.nextLine();
        for(i=0;i<s.length();i++)
           {
               if(s.charAt(i)!=t.charAt(i))
                    c++;
               else
                    continue;
            }
        System.out.println(c);   
    } main {
        Scanner obj=new Scanner(System.in);
        int i,c=0;String ns="";
        String s=obj.nextLine();
        String t=obj.nextLine();
        for(i=0;i<s.length();i++)
           {
               if(s.charAt(i)!=t.charAt(i))
                    c++;
               else
                    continue;
            }
        System.out.println(c);   
    } Scanner obj=new Scanner(System.in); obj new Scanner(System.in) int i i c=0; c 0 String ns=""; ns "" String s=obj.nextLine(); s obj.nextLine() obj.nextLine obj String t=obj.nextLine(); t obj.nextLine() obj.nextLine obj for(i=0;i<s.length();i++)
           {
               if(s.charAt(i)!=t.charAt(i))
                    c++;
               else
                    continue;
            } i=0; i=0 i 0 i<s.length() i s.length() s.length s i++ i++ i {
               if(s.charAt(i)!=t.charAt(i))
                    c++;
               else
                    continue;
            } {
               if(s.charAt(i)!=t.charAt(i))
                    c++;
               else
                    continue;
            } if(s.charAt(i)!=t.charAt(i))
                    c++;
               else
                    continue; s.charAt(i)!=t.charAt(i) s.charAt(i) s.charAt s i t.charAt(i) t.charAt t i c++ c continue; System.out.println(c) System.out.println System.out System System.out c String args[] args
import java.util.*;
import java.io.*;
class Main
{
    public static void main(String args[])throws IOException
    {
        Scanner obj=new Scanner(System.in);
        int i,c=0;String ns="";
        String s=obj.nextLine();
        String t=obj.nextLine();
        for(i=0;i<s.length();i++)
           {
               if(s.charAt(i)!=t.charAt(i))
                    c++;
               else
                    continue;
            }
        System.out.println(c);   
    }
}