import java.util.*;
public class Main {

    public static void main(String[] args)
    {
        Scanner in=new Scanner(System.in);
        String S = in.next();
        String T = in.next();
        int count = 0;
        if (S.length() == T.length()){
            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 public class Main {

    public static void main(String[] args)
    {
        Scanner in=new Scanner(System.in);
        String S = in.next();
        String T = in.next();
        int count = 0;
        if (S.length() == T.length()){
            for (int i = 0; i < S.length(); i++) {
                if (S.charAt(i) != T.charAt(i)){
                    count++;
                }
            }
            System.out.println(count);
        }
    }
} Main public static void main(String[] args)
    {
        Scanner in=new Scanner(System.in);
        String S = in.next();
        String T = in.next();
        int count = 0;
        if (S.length() == T.length()){
            for (int i = 0; i < S.length(); i++) {
                if (S.charAt(i) != T.charAt(i)){
                    count++;
                }
            }
            System.out.println(count);
        }
    } main {
        Scanner in=new Scanner(System.in);
        String S = in.next();
        String T = in.next();
        int count = 0;
        if (S.length() == T.length()){
            for (int i = 0; i < S.length(); i++) {
                if (S.charAt(i) != T.charAt(i)){
                    count++;
                }
            }
            System.out.println(count);
        }
    } Scanner in=new Scanner(System.in); in new Scanner(System.in) String S = in.next(); S in.next() in.next in String T = in.next(); T in.next() in.next in int count = 0; count 0 if (S.length() == T.length()){
            for (int i = 0; i < S.length(); i++) {
                if (S.charAt(i) != T.charAt(i)){
                    count++;
                }
            }
            System.out.println(count);
        } S.length() == T.length() S.length() S.length S T.length() T.length T {
            for (int i = 0; i < S.length(); i++) {
                if (S.charAt(i) != T.charAt(i)){
                    count++;
                }
            }
            System.out.println(count);
        } 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++ 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 in=new Scanner(System.in);
        String S = in.next();
        String T = in.next();
        int count = 0;
        if (S.length() == T.length()){
            for (int i = 0; i < S.length(); i++) {
                if (S.charAt(i) != T.charAt(i)){
                    count++;
                }
            }
            System.out.println(count);
        }
    }
} public class Main {

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

    public static void main(String[] args)
    {
        Scanner in=new Scanner(System.in);
        String S = in.next();
        String T = in.next();
        int count = 0;
        if (S.length() == T.length()){
            for (int i = 0; i < S.length(); i++) {
                if (S.charAt(i) != T.charAt(i)){
                    count++;
                }
            }
            System.out.println(count);
        }
    }
}
