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