#include <iostream>
#include <cmath>
#include <cstdio>
#include <cassert>

using namespace std;

//#define VISUALIZE

#ifdef VISUALIZE
#include <vector>
#include <utility>
static const double DELTA = 0.1;
#endif


double X[100000 + 1];
double Y[100000 + 1];

static const double EPS = 1e-4;
static const double G = 9.8;

double f(double x0, double y0, double v0, double theta, double x)
{
	return y0 + (x - x0) * tan(theta) - G * (x - x0) * (x - x0) / (2.0 * v0 * v0 * cos(theta) * cos(theta));
}

int main()
{
	int N;
	double V;
	while (cin >> N >> V && N){
		assert(1 <= N && N <= 10000);
		assert(1 <= V && V <= 10000);

		for (int i = 0; i < N; ++i){
			cin >> X[i] >> Y[i];
			assert(0 <= X[i] && X[i] <= 10000);
			assert(0 <= Y[i] && Y[i] <= 10000);

#ifdef VISUALIZE
			cout << X[i] << " " << Y[i] << endl;
#endif
		}
#ifdef VISUALIZE
		cout << endl << endl;
		vector<pair<double, double> > trajectory;
#endif
		X[N] = X[N - 1] + 1e-5;
		Y[N] = Y[N - 1] + 1e-5;

		double answer = 0;

		bool flying = false;
		double x0 = X[0];	//飛び始めた場所
		double y0 = Y[0];
		double theta;
		for (int i = 0; i < N - 1; ++i){
			if (flying){
				//飛んでる
				const double x1 = X[i + 1];
				const double y1 = Y[i + 1];
				const double xr = x1;
				const double yr = f(x0, y0, V, theta, xr);
				if (yr > Y[i + 1]){
#ifdef VISUALIZE
					for (double x = X[i]; x < X[i + 1]; x += DELTA){
						const double y = f(x0, y0, V, theta, x);
						trajectory.push_back(make_pair(x, y));
					}
#endif
					continue;
				}

				double l = X[i];
				double r = X[i + 1];
				const double a0 = (Y[i + 1] - Y[i]) / (X[i + 1] - X[i]);
				const double b0 = Y[i] - a0 * X[i];
				for (int loop = 0; loop < 50; ++loop){
					const double m = (l + r) * 0.5;
					const double y = f(x0, y0, V, theta, m);
					const double y2 = a0 * m + b0;
					if (y < y2){
						r = m;
					} else {
						l = m;
					}
				}

				const double x2 = (l + r) * 0.5;
				const double y2 = a0 * x2 + b0;

#ifdef VISUALIZE
					for (double x = X[i]; x < x2; x += DELTA){
						const double y = f(x0, y0, V, theta, x);
						trajectory.push_back(make_pair(x, y));
					}
					trajectory.push_back(make_pair(x2, f(x0, y0, V, theta, x2)));
					//trajectory.push_back(make_pair(X[i + 1], Y[i + 1]));
#endif

				if (x0 + EPS < x2 && X[i + 1] < x2 && x2 < X[i + 1] + EPS){
					fprintf(stderr, "#Warning! x0:%lf X[i]:%lf x:%lf y:%lf\n", x0, X[i], x2, y2);
				}

				if (X[i + 1] - EPS < x2 && x2 < X[i + 1]){
					fprintf(stderr, "#Warning! X[i + 1]:%lf x:%lf y:%lf\n", X[i + 1], x2, y2);
				}

				answer += hypot(X[i + 1] - x2, Y[i + 1] - y2);

			} else {
				//飛んでない
				answer += hypot(X[i + 1] - X[i], Y[i + 1] - Y[i]);
#ifdef VISUALIZE
				trajectory.push_back(make_pair(X[i], Y[i]));
#endif
			}

			flying = (Y[i + 1] - Y[i]) / (X[i + 1] - X[i]) > (Y[i + 2] - Y[i + 1]) / (X[i + 2] - X[i + 1]);
			if (flying){
				theta = atan2(Y[i + 1] - Y[i], X[i + 1] - X[i]);
				x0 = X[i + 1];
				y0 = Y[i + 1];
			}
		}

#ifndef VISUALIZE
		printf("%.20lf\n", answer);
#endif

#ifdef VISUALIZE
		if (!flying){
			trajectory.push_back(make_pair(X[N - 1], Y[N - 1]));
		}
		for (vector<pair<double, double> >::iterator it = trajectory.begin(); it != trajectory.end(); ++it){
			cout << it->first << " " << it->second << endl;
		}
		if (!flying){
			cout << X[N - 1] + 1 << " " << Y[N - 1] << endl;
		}
#endif
	}
}