import java.util.*;

public class Main {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String s = scanner.next();
        String t = scanner.next();
        int count = 0;
        char[] ss = s.toCharArray();
        char[] tt = t.toCharArray();

        for (int i = 0; i < s.length(); i++) {
            if (ss[i] != tt[i]) {
                count = count + 1;
            }
        }

        System.out.println(count);
    }
} import java.util.*; util.* java public class Main {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String s = scanner.next();
        String t = scanner.next();
        int count = 0;
        char[] ss = s.toCharArray();
        char[] tt = t.toCharArray();

        for (int i = 0; i < s.length(); i++) {
            if (ss[i] != tt[i]) {
                count = count + 1;
            }
        }

        System.out.println(count);
    }
} Main public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String s = scanner.next();
        String t = scanner.next();
        int count = 0;
        char[] ss = s.toCharArray();
        char[] tt = t.toCharArray();

        for (int i = 0; i < s.length(); i++) {
            if (ss[i] != tt[i]) {
                count = count + 1;
            }
        }

        System.out.println(count);
    } main {
        Scanner scanner = new Scanner(System.in);
        String s = scanner.next();
        String t = scanner.next();
        int count = 0;
        char[] ss = s.toCharArray();
        char[] tt = t.toCharArray();

        for (int i = 0; i < s.length(); i++) {
            if (ss[i] != tt[i]) {
                count = count + 1;
            }
        }

        System.out.println(count);
    } Scanner scanner = new Scanner(System.in); scanner new Scanner(System.in) String s = scanner.next(); s scanner.next() scanner.next scanner String t = scanner.next(); t scanner.next() scanner.next scanner int count = 0; count 0 char[] ss = s.toCharArray(); ss s.toCharArray() s.toCharArray s char[] tt = t.toCharArray(); tt t.toCharArray() t.toCharArray t for (int i = 0; i < s.length(); i++) {
            if (ss[i] != tt[i]) {
                count = count + 1;
            }
        } int i = 0; int i = 0; i 0 i < s.length() i s.length() s.length s i++ i++ i {
            if (ss[i] != tt[i]) {
                count = count + 1;
            }
        } {
            if (ss[i] != tt[i]) {
                count = count + 1;
            }
        } if (ss[i] != tt[i]) {
                count = count + 1;
            } ss[i] != tt[i] ss[i] ss i tt[i] tt i {
                count = count + 1;
            } count = count + 1 count count + 1 count 1 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 scanner = new Scanner(System.in);
        String s = scanner.next();
        String t = scanner.next();
        int count = 0;
        char[] ss = s.toCharArray();
        char[] tt = t.toCharArray();

        for (int i = 0; i < s.length(); i++) {
            if (ss[i] != tt[i]) {
                count = count + 1;
            }
        }

        System.out.println(count);
    }
} public class Main {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String s = scanner.next();
        String t = scanner.next();
        int count = 0;
        char[] ss = s.toCharArray();
        char[] tt = t.toCharArray();

        for (int i = 0; i < s.length(); i++) {
            if (ss[i] != tt[i]) {
                count = count + 1;
            }
        }

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

public class Main {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String s = scanner.next();
        String t = scanner.next();
        int count = 0;
        char[] ss = s.toCharArray();
        char[] tt = t.toCharArray();

        for (int i = 0; i < s.length(); i++) {
            if (ss[i] != tt[i]) {
                count = count + 1;
            }
        }

        System.out.println(count);
    }
}