import java.util.Scanner;
public class Main {

    public static void main(String[] args)
    {
        Scanner read = new Scanner(System.in);
        String s1 =read.next() , s2=read.next();
        int count=0;
        for (int i=0 ; i<s1.length() ; i++)
        {
            if (s1.charAt(i) == s2.charAt(i))
            {
                continue;
            }
            else {
                 count++;
             }
        }
        System.out.println(count);
    }
} import java.util.Scanner; Scanner java.util public class Main {

    public static void main(String[] args)
    {
        Scanner read = new Scanner(System.in);
        String s1 =read.next() , s2=read.next();
        int count=0;
        for (int i=0 ; i<s1.length() ; i++)
        {
            if (s1.charAt(i) == s2.charAt(i))
            {
                continue;
            }
            else {
                 count++;
             }
        }
        System.out.println(count);
    }
} Main public static void main(String[] args)
    {
        Scanner read = new Scanner(System.in);
        String s1 =read.next() , s2=read.next();
        int count=0;
        for (int i=0 ; i<s1.length() ; i++)
        {
            if (s1.charAt(i) == s2.charAt(i))
            {
                continue;
            }
            else {
                 count++;
             }
        }
        System.out.println(count);
    } main {
        Scanner read = new Scanner(System.in);
        String s1 =read.next() , s2=read.next();
        int count=0;
        for (int i=0 ; i<s1.length() ; i++)
        {
            if (s1.charAt(i) == s2.charAt(i))
            {
                continue;
            }
            else {
                 count++;
             }
        }
        System.out.println(count);
    } Scanner read = new Scanner(System.in); read new Scanner(System.in) String s1 =read.next() s1 read.next() read.next read s2=read.next(); s2 read.next() read.next read int count=0; count 0 for (int i=0 ; i<s1.length() ; i++)
        {
            if (s1.charAt(i) == s2.charAt(i))
            {
                continue;
            }
            else {
                 count++;
             }
        } 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))
            {
                continue;
            }
            else {
                 count++;
             }
        } {
            if (s1.charAt(i) == s2.charAt(i))
            {
                continue;
            }
            else {
                 count++;
             }
        } if (s1.charAt(i) == s2.charAt(i))
            {
                continue;
            }
            else {
                 count++;
             } s1.charAt(i) == s2.charAt(i) s1.charAt(i) s1.charAt s1 i s2.charAt(i) s2.charAt s2 i {
                continue;
            } continue; {
                 count++;
             } count++ count System.out.println(count) System.out.println System.out System System.out count String[] args args public class Main {

    public static void main(String[] args)
    {
        Scanner read = new Scanner(System.in);
        String s1 =read.next() , s2=read.next();
        int count=0;
        for (int i=0 ; i<s1.length() ; i++)
        {
            if (s1.charAt(i) == s2.charAt(i))
            {
                continue;
            }
            else {
                 count++;
             }
        }
        System.out.println(count);
    }
} public class Main {

    public static void main(String[] args)
    {
        Scanner read = new Scanner(System.in);
        String s1 =read.next() , s2=read.next();
        int count=0;
        for (int i=0 ; i<s1.length() ; i++)
        {
            if (s1.charAt(i) == s2.charAt(i))
            {
                continue;
            }
            else {
                 count++;
             }
        }
        System.out.println(count);
    }
} Main
import java.util.Scanner;
public class Main {

    public static void main(String[] args)
    {
        Scanner read = new Scanner(System.in);
        String s1 =read.next() , s2=read.next();
        int count=0;
        for (int i=0 ; i<s1.length() ; i++)
        {
            if (s1.charAt(i) == s2.charAt(i))
            {
                continue;
            }
            else {
                 count++;
             }
        }
        System.out.println(count);
    }
}