import java.io.IOException;
import java.util.Scanner;

public class Main {

public static void main(String[] args) throws IOException {
		Scanner scan = new Scanner(System.in);
		String s = scan.next();
  		String t = scan.next();
  	int cnt = 0;
  		for(int i=0; i<s.length(); i++){
          if(s.charAt(i) != t.charAt(i)){
            cnt++;
          }
          
        }
  
		System.out.println(cnt);
}
} import java.io.IOException; IOException java.io import java.util.Scanner; Scanner java.util public class Main {

public static void main(String[] args) throws IOException {
		Scanner scan = new Scanner(System.in);
		String s = scan.next();
  		String t = scan.next();
  	int cnt = 0;
  		for(int i=0; i<s.length(); i++){
          if(s.charAt(i) != t.charAt(i)){
            cnt++;
          }
          
        }
  
		System.out.println(cnt);
}
} Main public static void main(String[] args) throws IOException {
		Scanner scan = new Scanner(System.in);
		String s = scan.next();
  		String t = scan.next();
  	int cnt = 0;
  		for(int i=0; i<s.length(); i++){
          if(s.charAt(i) != t.charAt(i)){
            cnt++;
          }
          
        }
  
		System.out.println(cnt);
} main {
		Scanner scan = new Scanner(System.in);
		String s = scan.next();
  		String t = scan.next();
  	int cnt = 0;
  		for(int i=0; i<s.length(); i++){
          if(s.charAt(i) != t.charAt(i)){
            cnt++;
          }
          
        }
  
		System.out.println(cnt);
} Scanner scan = new Scanner(System.in); scan new Scanner(System.in) String s = scan.next(); s scan.next() scan.next scan String t = scan.next(); t scan.next() scan.next scan int cnt = 0; cnt 0 for(int i=0; i<s.length(); i++){
          if(s.charAt(i) != t.charAt(i)){
            cnt++;
          }
          
        } 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)){
            cnt++;
          }
          
        } {
          if(s.charAt(i) != t.charAt(i)){
            cnt++;
          }
          
        } if(s.charAt(i) != t.charAt(i)){
            cnt++;
          } s.charAt(i) != t.charAt(i) s.charAt(i) s.charAt s i t.charAt(i) t.charAt t i {
            cnt++;
          } cnt++ cnt System.out.println(cnt) System.out.println System.out System System.out cnt String[] args args public class Main {

public static void main(String[] args) throws IOException {
		Scanner scan = new Scanner(System.in);
		String s = scan.next();
  		String t = scan.next();
  	int cnt = 0;
  		for(int i=0; i<s.length(); i++){
          if(s.charAt(i) != t.charAt(i)){
            cnt++;
          }
          
        }
  
		System.out.println(cnt);
}
} public class Main {

public static void main(String[] args) throws IOException {
		Scanner scan = new Scanner(System.in);
		String s = scan.next();
  		String t = scan.next();
  	int cnt = 0;
  		for(int i=0; i<s.length(); i++){
          if(s.charAt(i) != t.charAt(i)){
            cnt++;
          }
          
        }
  
		System.out.println(cnt);
}
} Main
import java.io.IOException;
import java.util.Scanner;

public class Main {

public static void main(String[] args) throws IOException {
		Scanner scan = new Scanner(System.in);
		String s = scan.next();
  		String t = scan.next();
  	int cnt = 0;
  		for(int i=0; i<s.length(); i++){
          if(s.charAt(i) != t.charAt(i)){
            cnt++;
          }
          
        }
  
		System.out.println(cnt);
}
}
