Special Shop

Creatnx now wants to decorate his house with flower pots. He plans to buy exactly N ones. He can only buy them from Triracle's shop. There are only two kinds of flower pots available in that shop. The shop is very strange. If you buy 

$X$ flower pots of kind 1 then you must pay $A\times X^2$ and $B\times Y^2$ if you buy $Y$ flower pots of kind 2. Please help Creatnx buys exactly $N$ flower pots that minimize money he pays.

Example:

Input:  n = 5, a = 1, b = 2
Output: 17

Approach

C++

#include <bits/stdc++.h>
using namespace std;

void specialShop(long long n, long long a,
                 long long b)
{
    double p = (double)(n * b) / (a + b);
    p = round(p);
    long long ans = p * p * a + (n - p) * (n - p) * b;
    cout << ans << "\n";
}
int main()
{

    long long n = 5, a = 1, b = 2;

    specialShop(n, a, b);

    return 0;
}