#include <iostream>
#include <vector>
#include <string>
#include <set>
#include <random>
#include <iomanip>
#include <algorithm>

constexpr double PI = 3.1415926535898;

struct Pt
{
	int64_t x;
	int64_t y;

	bool operator<(const Pt& other) const
	{
		if (y == 0 && x <= 0)
		{
			if(other.y == 0 && other.x <= 0)
			{ 
				return x > other.x;
			}
			return true;
		}
		if (y > 0)
		{
			if (other.y == 0 && other.x <= 0)
			{
				return false;
			}
			if (other.y > 0)
			{
				int64_t det = x * other.y - other.x * y;
				if (det == 0)
				{
					return y < other.y;
				}
				return det < 0;
			}
			return true;
		}
		if (y == 0 && x >= 0)
		{
			if (other.y == 0 && other.x <= 0)
			{
				return false;
			}
			if (other.y > 0)
			{
				return false;
			}
			if (other.y == 0 && other.x > 0)
			{
				return x < other.x;
			}
			return true;
		}
		if (y < 0)
		{
			if (other.y < 0)
			{
				int64_t det = x * other.y - other.x * y;
				if (det == 0)
				{
					return y > other.y;
				}
				return det < 0;
			}
			return false;
		}
		return false;
	}
};

std::vector<double> probs;



int main()
{
	int n, k, d;
	std::cin >> n >> k >> d;
	char point;
	std::vector<Pt> points(n);
	for (int i = 0; i < n; i++)
	{
		int x1, x2, y1, y2;
		std::cin >> x1 >> point >> x2 >> y1 >> point >> y2;
		points[i].x = std::abs(x1) * 100LL + x2;
		points[i].y = std::abs(y1) * 100LL + y2;
		if (x1 < 0)
			points[i].x *= -1;
		if (y1 < 0)
			points[i].y *= -1;
	}

	if (k == 1)
	{
		std::cout << std::setprecision(30) << PI * d << std::endl;
		return 0;
	}

	probs.resize(n - 1);
	probs[n - 2] = double(k) * double(k - 1) / double(n) / double(n - 1);
	for (int i = n - 3; i >= k - 2; i--)
	{
		probs[i] = probs[i + 1] / double(i + 1) * double(i + 3 - k);
	}
	for (int i = k - 3; i >= 0; i--)
	{
		probs[i] = 0;
	}

	double tot = 0.0;

	for (int i = 0; i < n; i++)
	{
		std::vector<Pt> others;
		for (int j = 0; j < n; j++)
		{
			if (i != j)
			{
				others.push_back({ points[j].x - points[i].x, points[j].y - points[i].y });
			}
		}
		std::sort(others.begin(), others.end());		
		
		int opp = 0;
		for (int j = 0; j < n - 1; j++)
		{
			if (opp == j)
			{
				opp = (j + 1) % (n - 1);
			}
			
			while (true)
			{
				int64_t cross = others[j].x * others[opp].y - others[j].y * others[opp].x;
				int64_t dot = others[j].x * others[opp].x + others[j].y * others[opp].y;
				if (cross > 0)
					break;
				if (cross == 0 && dot > 0 && opp <= j)
					break;
				opp = (opp + 1) % (n - 1);
			}
			
			double len = 1e-2 * sqrt(double(others[j].x) * double(others[j].x) + double(others[j].y) * double(others[j].y));
			int cnt = (opp - j - 1 + (n - 1)) % (n - 1);
			if (cnt < 0)
				exit(-1);
			tot += len * probs[cnt];
		}
	}

	tot += PI * d;
	std::cout << std::setprecision(30) << tot << std::endl;
}