import java.util.Scanner;

public class Main {
  public static void main(String[] args) {
    String S, T;
    int cnt = 0;
    Scanner sc = new Scanner(System.in);

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

    S = sc.next();
    T = sc.next();
    for (int i = 0; i < S.length(); i++) {
      if (S.charAt(i) != T.charAt(i)) {
        cnt++;
      }
    }
    System.out.print(cnt);
  }
} Main public static void main(String[] args) {
    String S, T;
    int cnt = 0;
    Scanner sc = new Scanner(System.in);

    S = sc.next();
    T = sc.next();
    for (int i = 0; i < S.length(); i++) {
      if (S.charAt(i) != T.charAt(i)) {
        cnt++;
      }
    }
    System.out.print(cnt);
  } main {
    String S, T;
    int cnt = 0;
    Scanner sc = new Scanner(System.in);

    S = sc.next();
    T = sc.next();
    for (int i = 0; i < S.length(); i++) {
      if (S.charAt(i) != T.charAt(i)) {
        cnt++;
      }
    }
    System.out.print(cnt);
  } String S S T; T int cnt = 0; cnt 0 Scanner sc = new Scanner(System.in); sc new Scanner(System.in) S = sc.next() S sc.next() sc.next sc T = sc.next() T sc.next() sc.next sc 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.print(cnt) System.out.print System.out System System.out cnt String[] args args public class Main {
  public static void main(String[] args) {
    String S, T;
    int cnt = 0;
    Scanner sc = new Scanner(System.in);

    S = sc.next();
    T = sc.next();
    for (int i = 0; i < S.length(); i++) {
      if (S.charAt(i) != T.charAt(i)) {
        cnt++;
      }
    }
    System.out.print(cnt);
  }
} public class Main {
  public static void main(String[] args) {
    String S, T;
    int cnt = 0;
    Scanner sc = new Scanner(System.in);

    S = sc.next();
    T = sc.next();
    for (int i = 0; i < S.length(); i++) {
      if (S.charAt(i) != T.charAt(i)) {
        cnt++;
      }
    }
    System.out.print(cnt);
  }
} Main
import java.util.Scanner;

public class Main {
  public static void main(String[] args) {
    String S, T;
    int cnt = 0;
    Scanner sc = new Scanner(System.in);

    S = sc.next();
    T = sc.next();
    for (int i = 0; i < S.length(); i++) {
      if (S.charAt(i) != T.charAt(i)) {
        cnt++;
      }
    }
    System.out.print(cnt);
  }
}