Loops Calculate N! / (K! * (N-K)!)

using System;
using System.Numerics;
class NumberOfCombinations
{
    static void Main()
    {
        int N = int.Parse(Console.ReadLine());
        int K = int.Parse(Console.ReadLine());
        Combinations(N, K);
        Console.WriteLine(Combinations(N,K));
    }
    static BigInteger Combinations(int N, int K)
    {
        BigInteger factorialN = 1;
        BigInteger factorialK = 1;
        BigInteger factorialNK = 1;
        BigInteger resFactorials = 0;
        for (int i = 1; i <= N; i++)
        {
            factorialN = factorialN * i;
            if(i <= K)
            {
                factorialK = factorialK * i;
            }
            if(i <= N- K)
            {
                factorialNK = factorialNK * i;
            }
        }
        resFactorials = factorialK * factorialNK;
        return factorialN / resFactorials;
    }
}