#include <iostream>

using namespace std;

int main()
{
    float a;
    int n;
    float p;

    cout << "Enter a: ";
    cin >> a;
    cout << "Enter n: ";
    cin >> n;

    p = a;

    for (int i = 1; i < n; i++)
    {
        p *= (a + i);
    }

    cout << "P: " << p;

    return 0;
}