import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        char[] s = sc.nextLine().toCharArray();
        char[] t = sc.nextLine().toCharArray();
        int incorrect = 0;
        for(int i = 0;i < s.length;i++){
            if(s[i] != t[i]) incorrect++;
        }
        System.out.println(incorrect);
    }
} import java.util.*; util.* java public class Main {
    public static void main(String[] args) throws Exception {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        char[] s = sc.nextLine().toCharArray();
        char[] t = sc.nextLine().toCharArray();
        int incorrect = 0;
        for(int i = 0;i < s.length;i++){
            if(s[i] != t[i]) incorrect++;
        }
        System.out.println(incorrect);
    }
} Main public static void main(String[] args) throws Exception {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        char[] s = sc.nextLine().toCharArray();
        char[] t = sc.nextLine().toCharArray();
        int incorrect = 0;
        for(int i = 0;i < s.length;i++){
            if(s[i] != t[i]) incorrect++;
        }
        System.out.println(incorrect);
    } main {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        char[] s = sc.nextLine().toCharArray();
        char[] t = sc.nextLine().toCharArray();
        int incorrect = 0;
        for(int i = 0;i < s.length;i++){
            if(s[i] != t[i]) incorrect++;
        }
        System.out.println(incorrect);
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) char[] s = sc.nextLine().toCharArray(); s sc.nextLine().toCharArray() sc.nextLine().toCharArray sc.nextLine() sc.nextLine sc char[] t = sc.nextLine().toCharArray(); t sc.nextLine().toCharArray() sc.nextLine().toCharArray sc.nextLine() sc.nextLine sc int incorrect = 0; incorrect 0 for(int i = 0;i < s.length;i++){
            if(s[i] != t[i]) incorrect++;
        } 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]) incorrect++;
        } {
            if(s[i] != t[i]) incorrect++;
        } if(s[i] != t[i]) incorrect++; s[i] != t[i] s[i] s i t[i] t i incorrect++ incorrect System.out.println(incorrect) System.out.println System.out System System.out incorrect String[] args args public class Main {
    public static void main(String[] args) throws Exception {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        char[] s = sc.nextLine().toCharArray();
        char[] t = sc.nextLine().toCharArray();
        int incorrect = 0;
        for(int i = 0;i < s.length;i++){
            if(s[i] != t[i]) incorrect++;
        }
        System.out.println(incorrect);
    }
} public class Main {
    public static void main(String[] args) throws Exception {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        char[] s = sc.nextLine().toCharArray();
        char[] t = sc.nextLine().toCharArray();
        int incorrect = 0;
        for(int i = 0;i < s.length;i++){
            if(s[i] != t[i]) incorrect++;
        }
        System.out.println(incorrect);
    }
} Main
import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        // Your code here!
        Scanner sc = new Scanner(System.in);
        char[] s = sc.nextLine().toCharArray();
        char[] t = sc.nextLine().toCharArray();
        int incorrect = 0;
        for(int i = 0;i < s.length;i++){
            if(s[i] != t[i]) incorrect++;
        }
        System.out.println(incorrect);
    }
}
