#include <iostream>#include <math.h>#include <iomanip>using namespace std;#define eps 1e-8struct point { double x, y; }p[1010];double dist(point a, point b) { return sqrt((a.x - b.x)*(a.x - b.x) + (a.y - b.y) * (a.y - b.y)); }double get_K(point a, point b) { return (b.y - a.y) * 1.0 / (b.x - a.x); } point intersection(point u1, point u2, point v1, point v2) { point ret = u1; double t = ((u1.x - v1.x)*(v1.y - v2.y) - (u1.y - v1.y)*(v1.x - v2.x)) / ((u1.x - u2.x)*(v1.y - v2.y) - (u1.y - u2.y)*(v1.x - v2.x)); ret.x += (u2.x - u1.x)*t; ret.y += (u2.y - u1.y)*t; return ret; }int main() { int n; double h; while (cin >> n >> h && (n || h)) { p[0].x = 0, p[0].y = h; for (int i = 1; i <= n; i++) { cin >> p[i].x >> p[i].y; } double k = get_K(p[0], p[2]); double s = 1.0 * dist(p[1], p[2]); point mark = p[2]; for (int i = 3; i <= n; i++) { if (get_K(p[0], p[i]) > k) { k = get_K(p[0], p[i]); point inter = intersection(p[0], mark, p[i], p[i - 1]); s += dist(p[i], inter); mark = p[i]; } } cout <<fixed << setprecision(2) << s << endl; } }
