import 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;
        for(int i = 0;i<s.length();i++){
            if(s.charAt(i) != t.charAt(i)){
                count++;
            }
        }
        System.out.println(count);
    }
} import java.util.*; util.* java 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;
        for(int 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;
        for(int 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;
        for(int 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 for(int i = 0;i<s.length();i++){
            if(s.charAt(i) != t.charAt(i)){
                count++;
            }
        } int i = 0; int 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++ 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;
        for(int 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;
        for(int i = 0;i<s.length();i++){
            if(s.charAt(i) != t.charAt(i)){
                count++;
            }
        }
        System.out.println(count);
    }
} Main
import 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;
        for(int i = 0;i<s.length();i++){
            if(s.charAt(i) != t.charAt(i)){
                count++;
            }
        }
        System.out.println(count);
    }
}