import java.util.ArrayList;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Object o = run();
        if (o != null)
            System.out.println(o);
    }

    private static ArrayList<Integer> nScan(Scanner sc, int n) {
        ArrayList<Integer> al = new ArrayList<>();
        for (int i = 0; i < n; i++) {
            al.add(sc.nextInt());
        }
        return al;
    }

    private static Object run() {
        try (Scanner sc = new Scanner(System.in);) {
            int result = 0;
            char[] s = sc.next().toCharArray();
            char[] t = sc.next().toCharArray();
            //int y = sc.nextInt();
            //int t = sc.next();
            //ArrayList<Integer> x = nScan(sc, n);
            //ArrayList<Integer> y = nScan(sc, n);
            //ArrayList<String> s = nScan(sc, n);
            for (int i = 0; i < s.length; i++) {
                if (s[i] != t[i]) {
                    result++;
                }
            }
            return result;
        }
    }
} import java.util.ArrayList; ArrayList java.util import java.util.Scanner; Scanner java.util public class Main {
    public static void main(String[] args) {
        Object o = run();
        if (o != null)
            System.out.println(o);
    }

    private static ArrayList<Integer> nScan(Scanner sc, int n) {
        ArrayList<Integer> al = new ArrayList<>();
        for (int i = 0; i < n; i++) {
            al.add(sc.nextInt());
        }
        return al;
    }

    private static Object run() {
        try (Scanner sc = new Scanner(System.in);) {
            int result = 0;
            char[] s = sc.next().toCharArray();
            char[] t = sc.next().toCharArray();
            //int y = sc.nextInt();
            //int t = sc.next();
            //ArrayList<Integer> x = nScan(sc, n);
            //ArrayList<Integer> y = nScan(sc, n);
            //ArrayList<String> s = nScan(sc, n);
            for (int i = 0; i < s.length; i++) {
                if (s[i] != t[i]) {
                    result++;
                }
            }
            return result;
        }
    }
} Main public static void main(String[] args) {
        Object o = run();
        if (o != null)
            System.out.println(o);
    } main {
        Object o = run();
        if (o != null)
            System.out.println(o);
    } Object o = run(); o run() run if (o != null)
            System.out.println(o); o != null o null System.out.println(o) System.out.println System.out System System.out o String[] args args private static ArrayList<Integer> nScan(Scanner sc, int n) {
        ArrayList<Integer> al = new ArrayList<>();
        for (int i = 0; i < n; i++) {
            al.add(sc.nextInt());
        }
        return al;
    } nScan {
        ArrayList<Integer> al = new ArrayList<>();
        for (int i = 0; i < n; i++) {
            al.add(sc.nextInt());
        }
        return al;
    } ArrayList<Integer> al = new ArrayList<>(); al new ArrayList<>() for (int i = 0; i < n; i++) {
            al.add(sc.nextInt());
        } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
            al.add(sc.nextInt());
        } {
            al.add(sc.nextInt());
        } al.add(sc.nextInt()) al.add al sc.nextInt() sc.nextInt sc return al; al Scanner sc sc int n n private static Object run() {
        try (Scanner sc = new Scanner(System.in);) {
            int result = 0;
            char[] s = sc.next().toCharArray();
            char[] t = sc.next().toCharArray();
            //int y = sc.nextInt();
            //int t = sc.next();
            //ArrayList<Integer> x = nScan(sc, n);
            //ArrayList<Integer> y = nScan(sc, n);
            //ArrayList<String> s = nScan(sc, n);
            for (int i = 0; i < s.length; i++) {
                if (s[i] != t[i]) {
                    result++;
                }
            }
            return result;
        }
    } run {
        try (Scanner sc = new Scanner(System.in);) {
            int result = 0;
            char[] s = sc.next().toCharArray();
            char[] t = sc.next().toCharArray();
            //int y = sc.nextInt();
            //int t = sc.next();
            //ArrayList<Integer> x = nScan(sc, n);
            //ArrayList<Integer> y = nScan(sc, n);
            //ArrayList<String> s = nScan(sc, n);
            for (int i = 0; i < s.length; i++) {
                if (s[i] != t[i]) {
                    result++;
                }
            }
            return result;
        }
    } try (Scanner sc = new Scanner(System.in);) {
            int result = 0;
            char[] s = sc.next().toCharArray();
            char[] t = sc.next().toCharArray();
            //int y = sc.nextInt();
            //int t = sc.next();
            //ArrayList<Integer> x = nScan(sc, n);
            //ArrayList<Integer> y = nScan(sc, n);
            //ArrayList<String> s = nScan(sc, n);
            for (int i = 0; i < s.length; i++) {
                if (s[i] != t[i]) {
                    result++;
                }
            }
            return result;
        } {
            int result = 0;
            char[] s = sc.next().toCharArray();
            char[] t = sc.next().toCharArray();
            //int y = sc.nextInt();
            //int t = sc.next();
            //ArrayList<Integer> x = nScan(sc, n);
            //ArrayList<Integer> y = nScan(sc, n);
            //ArrayList<String> s = nScan(sc, n);
            for (int i = 0; i < s.length; i++) {
                if (s[i] != t[i]) {
                    result++;
                }
            }
            return result;
        } Scanner sc = new Scanner(System.in) Scanner sc = new Scanner(System.in) new Scanner(System.in) int result = 0; result 0 char[] s = sc.next().toCharArray(); s sc.next().toCharArray() sc.next().toCharArray sc.next() sc.next sc char[] t = sc.next().toCharArray(); t sc.next().toCharArray() sc.next().toCharArray sc.next() sc.next sc for (int i = 0; i < s.length; i++) {
                if (s[i] != t[i]) {
                    result++;
                }
            } int i = 0; int i = 0; i 0 i < s.length i s.length s s.length i++ i++ i {
                if (s[i] != t[i]) {
                    result++;
                }
            } {
                if (s[i] != t[i]) {
                    result++;
                }
            } if (s[i] != t[i]) {
                    result++;
                } s[i] != t[i] s[i] s i t[i] t i {
                    result++;
                } result++ result return result; result public class Main {
    public static void main(String[] args) {
        Object o = run();
        if (o != null)
            System.out.println(o);
    }

    private static ArrayList<Integer> nScan(Scanner sc, int n) {
        ArrayList<Integer> al = new ArrayList<>();
        for (int i = 0; i < n; i++) {
            al.add(sc.nextInt());
        }
        return al;
    }

    private static Object run() {
        try (Scanner sc = new Scanner(System.in);) {
            int result = 0;
            char[] s = sc.next().toCharArray();
            char[] t = sc.next().toCharArray();
            //int y = sc.nextInt();
            //int t = sc.next();
            //ArrayList<Integer> x = nScan(sc, n);
            //ArrayList<Integer> y = nScan(sc, n);
            //ArrayList<String> s = nScan(sc, n);
            for (int i = 0; i < s.length; i++) {
                if (s[i] != t[i]) {
                    result++;
                }
            }
            return result;
        }
    }
} public class Main {
    public static void main(String[] args) {
        Object o = run();
        if (o != null)
            System.out.println(o);
    }

    private static ArrayList<Integer> nScan(Scanner sc, int n) {
        ArrayList<Integer> al = new ArrayList<>();
        for (int i = 0; i < n; i++) {
            al.add(sc.nextInt());
        }
        return al;
    }

    private static Object run() {
        try (Scanner sc = new Scanner(System.in);) {
            int result = 0;
            char[] s = sc.next().toCharArray();
            char[] t = sc.next().toCharArray();
            //int y = sc.nextInt();
            //int t = sc.next();
            //ArrayList<Integer> x = nScan(sc, n);
            //ArrayList<Integer> y = nScan(sc, n);
            //ArrayList<String> s = nScan(sc, n);
            for (int i = 0; i < s.length; i++) {
                if (s[i] != t[i]) {
                    result++;
                }
            }
            return result;
        }
    }
} Main
import java.util.ArrayList;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Object o = run();
        if (o != null)
            System.out.println(o);
    }

    private static ArrayList<Integer> nScan(Scanner sc, int n) {
        ArrayList<Integer> al = new ArrayList<>();
        for (int i = 0; i < n; i++) {
            al.add(sc.nextInt());
        }
        return al;
    }

    private static Object run() {
        try (Scanner sc = new Scanner(System.in);) {
            int result = 0;
            char[] s = sc.next().toCharArray();
            char[] t = sc.next().toCharArray();
            //int y = sc.nextInt();
            //int t = sc.next();
            //ArrayList<Integer> x = nScan(sc, n);
            //ArrayList<Integer> y = nScan(sc, n);
            //ArrayList<String> s = nScan(sc, n);
            for (int i = 0; i < s.length; i++) {
                if (s[i] != t[i]) {
                    result++;
                }
            }
            return result;
        }
    }
}