

import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        // TODO 自動生成されたメソッド・スタブ
        Scanner sc = new Scanner(System.in);
        String s = sc.next();
        String t = sc.next();

        int rtn = 0;
        for (int i = 0; i < s.length(); i++) {
            if (String.valueOf(s.charAt(i)).equals(String.valueOf(t.charAt(i)))) {
                continue;
            }
            rtn++;
        }
        System.out.println(rtn);
    }

} import java.util.Scanner; Scanner java.util public class Main {

    public static void main(String[] args) {
        // TODO 自動生成されたメソッド・スタブ
        Scanner sc = new Scanner(System.in);
        String s = sc.next();
        String t = sc.next();

        int rtn = 0;
        for (int i = 0; i < s.length(); i++) {
            if (String.valueOf(s.charAt(i)).equals(String.valueOf(t.charAt(i)))) {
                continue;
            }
            rtn++;
        }
        System.out.println(rtn);
    }

} Main public static void main(String[] args) {
        // TODO 自動生成されたメソッド・スタブ
        Scanner sc = new Scanner(System.in);
        String s = sc.next();
        String t = sc.next();

        int rtn = 0;
        for (int i = 0; i < s.length(); i++) {
            if (String.valueOf(s.charAt(i)).equals(String.valueOf(t.charAt(i)))) {
                continue;
            }
            rtn++;
        }
        System.out.println(rtn);
    } main {
        // TODO 自動生成されたメソッド・スタブ
        Scanner sc = new Scanner(System.in);
        String s = sc.next();
        String t = sc.next();

        int rtn = 0;
        for (int i = 0; i < s.length(); i++) {
            if (String.valueOf(s.charAt(i)).equals(String.valueOf(t.charAt(i)))) {
                continue;
            }
            rtn++;
        }
        System.out.println(rtn);
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) String s = sc.next(); s sc.next() sc.next sc String t = sc.next(); t sc.next() sc.next sc int rtn = 0; rtn 0 for (int i = 0; i < s.length(); i++) {
            if (String.valueOf(s.charAt(i)).equals(String.valueOf(t.charAt(i)))) {
                continue;
            }
            rtn++;
        } int i = 0; int i = 0; i 0 i < s.length() i s.length() s.length s i++ i++ i {
            if (String.valueOf(s.charAt(i)).equals(String.valueOf(t.charAt(i)))) {
                continue;
            }
            rtn++;
        } {
            if (String.valueOf(s.charAt(i)).equals(String.valueOf(t.charAt(i)))) {
                continue;
            }
            rtn++;
        } if (String.valueOf(s.charAt(i)).equals(String.valueOf(t.charAt(i)))) {
                continue;
            } String.valueOf(s.charAt(i)).equals(String.valueOf(t.charAt(i))) String.valueOf(s.charAt(i)).equals String.valueOf(s.charAt(i)) String.valueOf String s.charAt(i) s.charAt s i String.valueOf(t.charAt(i)) String.valueOf String t.charAt(i) t.charAt t i {
                continue;
            } continue; rtn++ rtn System.out.println(rtn) System.out.println System.out System System.out rtn String[] args args public class Main {

    public static void main(String[] args) {
        // TODO 自動生成されたメソッド・スタブ
        Scanner sc = new Scanner(System.in);
        String s = sc.next();
        String t = sc.next();

        int rtn = 0;
        for (int i = 0; i < s.length(); i++) {
            if (String.valueOf(s.charAt(i)).equals(String.valueOf(t.charAt(i)))) {
                continue;
            }
            rtn++;
        }
        System.out.println(rtn);
    }

} public class Main {

    public static void main(String[] args) {
        // TODO 自動生成されたメソッド・スタブ
        Scanner sc = new Scanner(System.in);
        String s = sc.next();
        String t = sc.next();

        int rtn = 0;
        for (int i = 0; i < s.length(); i++) {
            if (String.valueOf(s.charAt(i)).equals(String.valueOf(t.charAt(i)))) {
                continue;
            }
            rtn++;
        }
        System.out.println(rtn);
    }

} Main


import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        // TODO 自動生成されたメソッド・スタブ
        Scanner sc = new Scanner(System.in);
        String s = sc.next();
        String t = sc.next();

        int rtn = 0;
        for (int i = 0; i < s.length(); i++) {
            if (String.valueOf(s.charAt(i)).equals(String.valueOf(t.charAt(i)))) {
                continue;
            }
            rtn++;
        }
        System.out.println(rtn);
    }

}
