1 #include <iostream>  2 #include<cstdio>  3 #include<cstring>  4 #include<algorithm>  5 #include<stdlib.h>  6 #include<vector>  7 #include<cmath>  8 #include<queue>  9 #include<set> 10 using namespace std; 11 #define N 100 12 #define LL long long 13 #define INF 0xfffffff 14 const double eps = 1e-8; 15 const double pi = acos(-1.0); 16 const double inf = ~0u>>2; 17 struct point 18 { 19     double x,y; 20     point(double x=0,double y=0):x(x),y(y){} 21 }p[N]; 22 struct line 23 { 24     point u,v; 25 }li[N]; 26 double w[N][N]; 27 typedef point pointt; 28 pointt operator - (point a,point b) 29 { 30     return pointt(a.x-b.x,a.y-b.y); 31 } 32 int dcmp(double x) 33 { 34     if(fabs(x)<eps) return 0; 35     return x<0?-1:1; 36 } 37 double dis(point a) 38 { 39     return sqrt(a.x*a.x+a.y*a.y); 40 } 41 double cross(point a,point b) 42 { 43     return a.x*b.y-a.y*b.x; 44 } 45 bool segprointer(point a1,point a2,point b1,point b2) 46 { 47     double c1 = cross(a2-a1,b1-a1),c2 = cross(a2-a1,b2-a1), 48     c3  = cross(b2-b1,a1-b1),c4 = cross(b2-b1,a2-b1); 49     return dcmp(c1)*dcmp(c2)<0&&dcmp(c3)*dcmp(c4)<0; 50 } 51 int main() 52 { 53     int n,i,j,k; 54     while(scanf("%d",&n)!=EOF) 55     { 56         if(n==-1) break; 57         int g = 0; 58         for(i = 1; i <= 100 ; i++) 59         { 60             for(j = 1;  j<= 100 ; j++) 61             w[i][j] = INF; 62             w[i][i] = 0; 63         } 64         int o = 0; 65         for(i = 1; i <= n ;i++) 66         { 67             double k; 68             scanf("%lf",&k); 69             for(j = 1; j <= 4; j++) 70             { 71                 p[++g].x = k; 72                 scanf("%lf",&p[g].y); 73             } 74             point pp = point(k,0); 75             li[++o].u = pp; 76             li[o].v = p[g-3]; 77             li[++o].u = p[g-2]; 78             li[o].v = p[g-1]; 79             li[++o].u = p[g]; 80             pp = point(k,10); 81             li[o].v = pp; 82         } 83         p[g+1] = point(0,5); 84         p[g+2] = point(10,5); 85         //printf("%d\n",segprointer(p[g+1],p[g+2],li[5].u,li[5].v)); 86         for(i = 1; i <= g+2; i++) 87             for(j = i+1; j <= g+2; j++) 88             { 89                 if(i==j) continue; 90                 for(k = 1; k <= o ; k++) 91                 { 92                     if(segprointer(p[i],p[j],li[k].u,li[k].v))break; 93  94                 } 95                 if(k>o) 96                 w[i][j] = w[j][i] = dis(p[i]-p[j]); 97                 //printf("%.2f %.2f %.2f %.2f %.2f\n",p[i].x,p[i].y,p[j].x,p[j].y,w[i][j]); 98             } 99         for(i = 1; i <= g+2 ; i++)100             for(j = 1; j <=g+2 ;j++)101                 for(k = 1; k <= g+2 ; k++)102                 w[j][k] = min(w[j][i]+w[i][k],w[j][k]);103         printf("%.2f\n",w[g+1][g+2]);104     }105     return 0;106 }