import java.util.*;

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

  }
}
