import java.util.*;
import java.util.Arrays;

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

    }
} import java.util.*; util.* java import java.util.Arrays; Arrays java.util public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        
        String s = sc.nextLine();
        String t = sc.nextLine();
        
        int count = 0, i;
        for(i = 0; i < s.length(); i++){
            if(s.charAt(i) != t.charAt(i)) count++;
        }
        System.out.println(count);

    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        
        String s = sc.nextLine();
        String t = sc.nextLine();
        
        int count = 0, i;
        for(i = 0; i < s.length(); i++){
            if(s.charAt(i) != t.charAt(i)) count++;
        }
        System.out.println(count);

    } main {
        Scanner sc = new Scanner(System.in);
        
        String s = sc.nextLine();
        String t = sc.nextLine();
        
        int count = 0, i;
        for(i = 0; i < s.length(); i++){
            if(s.charAt(i) != t.charAt(i)) count++;
        }
        System.out.println(count);

    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) String s = sc.nextLine(); s sc.nextLine() sc.nextLine sc String t = sc.nextLine(); t sc.nextLine() sc.nextLine sc int count = 0 count 0 i; i for(i = 0; i < s.length(); i++){
            if(s.charAt(i) != t.charAt(i)) count++;
        } i = 0; i = 0 i 0 i < s.length() i s.length() s.length s i++ i++ i {
            if(s.charAt(i) != t.charAt(i)) count++;
        } {
            if(s.charAt(i) != t.charAt(i)) count++;
        } if(s.charAt(i) != t.charAt(i)) count++; s.charAt(i) != t.charAt(i) s.charAt(i) s.charAt s i t.charAt(i) t.charAt t i count++ count 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 sc = new Scanner(System.in);
        
        String s = sc.nextLine();
        String t = sc.nextLine();
        
        int count = 0, i;
        for(i = 0; i < s.length(); i++){
            if(s.charAt(i) != t.charAt(i)) count++;
        }
        System.out.println(count);

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

    }
} Main
import java.util.*;
import java.util.Arrays;

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

    }
}