#include <iostream>#include <cstdio>#include <cmath>#include <algorithm>using namespace std;const double eps = 1e-8;struct Point { double x, y;};struct Line { Point a, b;} house, pro;struct Obstruction { Point a, b; double lview, rview;};int dblcmp(double k) { if (fabs(k) < eps) return 0; return k > 0 ? 1 : -1;}double getXByY(Point a, Point b, double y) { return (y-a.y)*(a.x-b.x)/(a.y-b.y)+a.x;}bool cmp(const Obstruction& obs1, const Obstruction& obs2) { return dblcmp(obs1.lview-obs2.lview) <= 0;}int main(){ double x1, x2, y, tmp, ans; int n, i, id, k; while (scanf ("%lf%lf%lf", &x1, &x2, &y)) { if (!dblcmp(x1) && !dblcmp(x2) && !dblcmp(y)) break; house.a.x = x1; house.b.x = x2; house.a.y = house.b.y = y; scanf ("%lf%lf%lfn%d", &pro.a.x, &pro.b.x, &pro.a.y, &n); pro.b.y = pro.a.y; Obstruction* obs = new Obstruction[n]; id = 0; for (i = 0; i < n; i++) { scanf ("%lf%lf%lf", &x1, &x2, &y); if (dblcmp(y-house.a.y) >= 0 || dblcmp(y-pro.a.y) <= 0) continue; obs[id].a.x = x1; obs[id].b.x = x2; obs[id].a.y = obs[id].b.y = y; obs[id].lview = getXByY(house.b, obs[id].a, pro.a.y); obs[id].rview = getXByY(house.a, obs[id].b, pro.a.y); id++; } sort(obs, obs+id, cmp); //按lview排序 ans = 0; if (dblcmp(obs[0].lview-pro.a.x) > 0) ans = obs[0].lview-pro.a.x; if (dblcmp(obs[0].rview-pro.a.x) < 0) obs[0].rview = pro.a.x; k = 0; for (i = 1; i < id; i++) { if (dblcmp(obs[k].rview-pro.b.x) >= 0) break; tmp = obs[i].lview-obs[k].rview; if (dblcmp(tmp) > 0) { k = i; if (dblcmp(tmp-ans) > 0) ans = tmp; } else if (dblcmp(obs[i].rview-obs[k].rview) > 0) k = i; } tmp = pro.b.x - obs[k].rview; if (dblcmp(tmp-ans) > 0) ans = tmp; if (dblcmp(ans) > 0) printf ("%.2lfn", ans); else printf ("No Viewn"); delete [] obs; } return 0;}
