#include <cstdlib> #include <algorithm> #include <cstdlib> #include <cmath>#include <cstdlib> #include <algorithm> #include <cstdlib> #include <cstdio>const double EPS = 1e-4;const int MAXN = 512;inline bool lt(double a, double b) { return a < b - EPS;}inline bool gt(double a, double b) { return a > b + EPS;}inline bool eq(double a, double b) { return fabs(a - b) < EPS;}int main() { int ri = 0, n, p, q; bool flag; double t, r, dr, tr, alpha, beta, gamma; double x[MAXN], y[MAXN]; while (scanf("%d%lf", &n, &r) != EOF && r > 0) { x[0] = y[0] = 0; p = 0; alpha = -M_PI; for (int i = 1; i <= n; ++i) { scanf("%lf%lf", &x[i], &y[i]); } t = 0; while (true) { q = -1; for (int i = 1; i <= n; ++i) { if (i == p) { continue; } tr = hypot(y[i] - y[p], x[i] - x[p]); gamma = atan2(y[i] - y[p], x[i] - x[p]); if (!lt(tr, r)) { continue; } flag = false; if (q == -1) { flag = true; } else if (eq(gamma, beta)) { flag = gt(tr, dr); } else if (lt(gamma, alpha)) { flag = lt(beta, alpha) && lt(gamma, beta); } else if (gt(gamma, alpha)) { flag = lt(beta, alpha) || lt(gamma, beta); } if (flag) { q = i; dr = tr; beta = gamma; } } flag = false; if (gt(y[p] + r, 0)) { gamma = asin(-y[p] / r); if (q == -1 || (lt(alpha, gamma) && lt(gamma, beta)) || (gt(alpha, beta) && (gt(gamma, alpha) || lt(gamma, beta)))) { q = -1; beta = gamma; flag = true; } } if (q != -1 || flag) { if (lt(alpha, beta)) { t += r * (beta - alpha); } else if (lt(beta, alpha)) {t += r * (beta - alpha + 2 * M_PI); } else { } } if (q != -1) { p = q; r -= dr; alpha = beta; continue; } printf("Pendulum #%dnLength of periodic orbit = ", ++ri); printf("%.2lfnn", flag ? 2 * t : 2 * M_PI * r); break; } } return 0;}
