import java.util.Scanner;

public class Main {
    static Scanner stdIn = new Scanner(System.in);
    public static void main(String[] args){
        char[] s = stdIn.next().toCharArray();
        char[] t = stdIn.next().toCharArray();

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

        System.out.println(counter);
    }
} import java.util.Scanner; Scanner java.util public class Main {
    static Scanner stdIn = new Scanner(System.in);
    public static void main(String[] args){
        char[] s = stdIn.next().toCharArray();
        char[] t = stdIn.next().toCharArray();

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

        System.out.println(counter);
    }
} Main static Scanner stdIn = new Scanner(System.in); stdIn new Scanner(System.in) public static void main(String[] args){
        char[] s = stdIn.next().toCharArray();
        char[] t = stdIn.next().toCharArray();

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

        System.out.println(counter);
    } main {
        char[] s = stdIn.next().toCharArray();
        char[] t = stdIn.next().toCharArray();

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

        System.out.println(counter);
    } char[] s = stdIn.next().toCharArray(); s stdIn.next().toCharArray() stdIn.next().toCharArray stdIn.next() stdIn.next stdIn char[] t = stdIn.next().toCharArray(); t stdIn.next().toCharArray() stdIn.next().toCharArray stdIn.next() stdIn.next stdIn int counter = 0; counter 0 int n = s.length; n s.length s s.length for(int i=0; i<n; i++){
            if(s[i] != t[i])
                counter++;
        } int i=0; int i=0; i 0 i<n i n i++ i++ i {
            if(s[i] != t[i])
                counter++;
        } {
            if(s[i] != t[i])
                counter++;
        } if(s[i] != t[i])
                counter++; s[i] != t[i] s[i] s i t[i] t i counter++ counter System.out.println(counter) System.out.println System.out System System.out counter String[] args args public class Main {
    static Scanner stdIn = new Scanner(System.in);
    public static void main(String[] args){
        char[] s = stdIn.next().toCharArray();
        char[] t = stdIn.next().toCharArray();

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

        System.out.println(counter);
    }
} public class Main {
    static Scanner stdIn = new Scanner(System.in);
    public static void main(String[] args){
        char[] s = stdIn.next().toCharArray();
        char[] t = stdIn.next().toCharArray();

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

        System.out.println(counter);
    }
} Main
import java.util.Scanner;

public class Main {
    static Scanner stdIn = new Scanner(System.in);
    public static void main(String[] args){
        char[] s = stdIn.next().toCharArray();
        char[] t = stdIn.next().toCharArray();

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

        System.out.println(counter);
    }
}
