import java.util.Scanner;
public class Main {
  
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    String S = sc.next();
    String T = sc.next();
    int num = S.length();
    int counts = 0;
    for (int i = 0; i < num; i++) {
      if (S.charAt(i) != T.charAt(i)) {
        counts = counts + 1;
      }
    }
    System.out.println(counts);
  }
} import java.util.Scanner; Scanner 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 num = S.length();
    int counts = 0;
    for (int i = 0; i < num; i++) {
      if (S.charAt(i) != T.charAt(i)) {
        counts = counts + 1;
      }
    }
    System.out.println(counts);
  }
} Main public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    String S = sc.next();
    String T = sc.next();
    int num = S.length();
    int counts = 0;
    for (int i = 0; i < num; i++) {
      if (S.charAt(i) != T.charAt(i)) {
        counts = counts + 1;
      }
    }
    System.out.println(counts);
  } main {
    Scanner sc = new Scanner(System.in);
    String S = sc.next();
    String T = sc.next();
    int num = S.length();
    int counts = 0;
    for (int i = 0; i < num; i++) {
      if (S.charAt(i) != T.charAt(i)) {
        counts = counts + 1;
      }
    }
    System.out.println(counts);
  } 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 num = S.length(); num S.length() S.length S int counts = 0; counts 0 for (int i = 0; i < num; i++) {
      if (S.charAt(i) != T.charAt(i)) {
        counts = counts + 1;
      }
    } int i = 0; int i = 0; i 0 i < num i num i++ i++ i {
      if (S.charAt(i) != T.charAt(i)) {
        counts = counts + 1;
      }
    } {
      if (S.charAt(i) != T.charAt(i)) {
        counts = counts + 1;
      }
    } if (S.charAt(i) != T.charAt(i)) {
        counts = counts + 1;
      } S.charAt(i) != T.charAt(i) S.charAt(i) S.charAt S i T.charAt(i) T.charAt T i {
        counts = counts + 1;
      } counts = counts + 1 counts counts + 1 counts 1 System.out.println(counts) System.out.println System.out System System.out counts 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 num = S.length();
    int counts = 0;
    for (int i = 0; i < num; i++) {
      if (S.charAt(i) != T.charAt(i)) {
        counts = counts + 1;
      }
    }
    System.out.println(counts);
  }
} public class Main {
  
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    String S = sc.next();
    String T = sc.next();
    int num = S.length();
    int counts = 0;
    for (int i = 0; i < num; i++) {
      if (S.charAt(i) != T.charAt(i)) {
        counts = counts + 1;
      }
    }
    System.out.println(counts);
  }
} Main
import java.util.Scanner;
public class Main {
  
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    String S = sc.next();
    String T = sc.next();
    int num = S.length();
    int counts = 0;
    for (int i = 0; i < num; i++) {
      if (S.charAt(i) != T.charAt(i)) {
        counts = counts + 1;
      }
    }
    System.out.println(counts);
  }
}
