import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
 
        String s[] = sc.next().split("");
        String t[] = sc.next().split("");
        int count = 0;

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

        System.out.println(String.valueOf(count));
    }
} import java.util.Scanner; Scanner java.util public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
 
        String s[] = sc.next().split("");
        String t[] = sc.next().split("");
        int count = 0;

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

        System.out.println(String.valueOf(count));
    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
 
        String s[] = sc.next().split("");
        String t[] = sc.next().split("");
        int count = 0;

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

        System.out.println(String.valueOf(count));
    } main {
        Scanner sc = new Scanner(System.in);
 
        String s[] = sc.next().split("");
        String t[] = sc.next().split("");
        int count = 0;

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

        System.out.println(String.valueOf(count));
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) String s[] = sc.next().split(""); s sc.next().split("") sc.next().split sc.next() sc.next sc "" String t[] = sc.next().split(""); t sc.next().split("") sc.next().split sc.next() sc.next sc "" int count = 0; count 0 for(int i = 0; i < s.length; i++) {
            if(!s[i].equals(t[i])) {
                count++;
            }
        } int i = 0; int i = 0; i 0 i < s.length i s.length s s.length i++ i++ i {
            if(!s[i].equals(t[i])) {
                count++;
            }
        } {
            if(!s[i].equals(t[i])) {
                count++;
            }
        } if(!s[i].equals(t[i])) {
                count++;
            } !s[i].equals(t[i]) s[i].equals(t[i]) s[i].equals s[i] s i t[i] t i {
                count++;
            } count++ count System.out.println(String.valueOf(count)) System.out.println System.out System System.out String.valueOf(count) String.valueOf String count String[] args args public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
 
        String s[] = sc.next().split("");
        String t[] = sc.next().split("");
        int count = 0;

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

        System.out.println(String.valueOf(count));
    }
} public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
 
        String s[] = sc.next().split("");
        String t[] = sc.next().split("");
        int count = 0;

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

        System.out.println(String.valueOf(count));
    }
} Main
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
 
        String s[] = sc.next().split("");
        String t[] = sc.next().split("");
        int count = 0;

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

        System.out.println(String.valueOf(count));
    }
}