Inverted arrow by ' * ' in 3 for loops ;(

/*
    *
   **
  ***
 ****
*****

*****
 ****
  ***
   **
    *
*/
#include <iostream>

using std::cout;
using std::cin;
using std::endl;

void main()
{
    setlocale(LC_ALL, "Russian");

    int a, b = 0;

    cout << "Введите размер: "; cin >> a;

    a *= 2;

    for (int i = 0; i < a; i++, ((i == (a / 2)) ? cout << endl << endl : cout << endl))
    {
        if (i < (a / 2)) b++; else if (i == (a / 2)) b = a / 2; else b--;
        for (int j = (a / 2) + 1; j > b; j--, cout << " "); // выравнивание
        for (int k = 0; k < b; k++, cout << '*');
    }
}