import java.util.Scanner;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    
    String text1 = sc.next();
    String text2 = sc.next();
    
    char[] c1 = new char[text1.length()];
    char[] c2 = new char[text2.length()];
    
    int count = 0;
    for (int i = 0; i < text1.length(); i++) {
      	c1[i] = text1.charAt(i);
      	c2[i] = text2.charAt(i);
      
      	if (c1[i] != c2[i]) {
          count++;
        }
    }
    System.out.println(count);
  }
} import java.util.Scanner; Scanner java.util public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    
    String text1 = sc.next();
    String text2 = sc.next();
    
    char[] c1 = new char[text1.length()];
    char[] c2 = new char[text2.length()];
    
    int count = 0;
    for (int i = 0; i < text1.length(); i++) {
      	c1[i] = text1.charAt(i);
      	c2[i] = text2.charAt(i);
      
      	if (c1[i] != c2[i]) {
          count++;
        }
    }
    System.out.println(count);
  }
} Main public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    
    String text1 = sc.next();
    String text2 = sc.next();
    
    char[] c1 = new char[text1.length()];
    char[] c2 = new char[text2.length()];
    
    int count = 0;
    for (int i = 0; i < text1.length(); i++) {
      	c1[i] = text1.charAt(i);
      	c2[i] = text2.charAt(i);
      
      	if (c1[i] != c2[i]) {
          count++;
        }
    }
    System.out.println(count);
  } main {
    Scanner sc = new Scanner(System.in);
    
    String text1 = sc.next();
    String text2 = sc.next();
    
    char[] c1 = new char[text1.length()];
    char[] c2 = new char[text2.length()];
    
    int count = 0;
    for (int i = 0; i < text1.length(); i++) {
      	c1[i] = text1.charAt(i);
      	c2[i] = text2.charAt(i);
      
      	if (c1[i] != c2[i]) {
          count++;
        }
    }
    System.out.println(count);
  } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) String text1 = sc.next(); text1 sc.next() sc.next sc String text2 = sc.next(); text2 sc.next() sc.next sc char[] c1 = new char[text1.length()]; c1 new char[text1.length()] text1.length() text1.length text1 char[] c2 = new char[text2.length()]; c2 new char[text2.length()] text2.length() text2.length text2 int count = 0; count 0 for (int i = 0; i < text1.length(); i++) {
      	c1[i] = text1.charAt(i);
      	c2[i] = text2.charAt(i);
      
      	if (c1[i] != c2[i]) {
          count++;
        }
    } int i = 0; int i = 0; i 0 i < text1.length() i text1.length() text1.length text1 i++ i++ i {
      	c1[i] = text1.charAt(i);
      	c2[i] = text2.charAt(i);
      
      	if (c1[i] != c2[i]) {
          count++;
        }
    } {
      	c1[i] = text1.charAt(i);
      	c2[i] = text2.charAt(i);
      
      	if (c1[i] != c2[i]) {
          count++;
        }
    } c1[i] = text1.charAt(i) c1[i] c1 i text1.charAt(i) text1.charAt text1 i c2[i] = text2.charAt(i) c2[i] c2 i text2.charAt(i) text2.charAt text2 i if (c1[i] != c2[i]) {
          count++;
        } c1[i] != c2[i] c1[i] c1 i c2[i] c2 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 text1 = sc.next();
    String text2 = sc.next();
    
    char[] c1 = new char[text1.length()];
    char[] c2 = new char[text2.length()];
    
    int count = 0;
    for (int i = 0; i < text1.length(); i++) {
      	c1[i] = text1.charAt(i);
      	c2[i] = text2.charAt(i);
      
      	if (c1[i] != c2[i]) {
          count++;
        }
    }
    System.out.println(count);
  }
} public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    
    String text1 = sc.next();
    String text2 = sc.next();
    
    char[] c1 = new char[text1.length()];
    char[] c2 = new char[text2.length()];
    
    int count = 0;
    for (int i = 0; i < text1.length(); i++) {
      	c1[i] = text1.charAt(i);
      	c2[i] = text2.charAt(i);
      
      	if (c1[i] != c2[i]) {
          count++;
        }
    }
    System.out.println(count);
  }
} Main
import java.util.Scanner;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    
    String text1 = sc.next();
    String text2 = sc.next();
    
    char[] c1 = new char[text1.length()];
    char[] c2 = new char[text2.length()];
    
    int count = 0;
    for (int i = 0; i < text1.length(); i++) {
      	c1[i] = text1.charAt(i);
      	c2[i] = text2.charAt(i);
      
      	if (c1[i] != c2[i]) {
          count++;
        }
    }
    System.out.println(count);
  }
}