Average arrays

#include<iostream>
using namespace std;

main()
{
   int arrayOne[20], arrayTwo[20], a, b;

// The user is asked for the number of elements in the array
   cout << "How many elements are in the array? ";
   cin >> b;

   cout << "Please type the elements in array 1" << endl;

   for ( a = 0 ; a < b ; a++ )
      cin >> arrayOne[a];

   cout << "Please type the elements in array 2 " << endl;

   for ( a = 0 ; a < b ; a++ )
      cin >> arrayTwo[a];

   cout << "The average of elements of two arrays " << endl;

   for ( a = 0 ; a < b ; a++ )
      cout << float(arrayOne[a] + arrayTwo[a])/2 << endl;

   return 0;
}