/*dij+两点间距离*/#include<stdio.h>#include<string.h>#include<stdlib.h>#include<algorithm>#include<iostream>#include<math.h>using namespace std;const int maxn = 205;//point numberconst int maxm = 105;//line numberconst double inf = 99999999;const double eps = 1e-8;struct POINT{double x,y;int f;}S,T;struct LINE{double x1,y1,x2,y2;int f;};int cnt_line,cnt_point;POINT point[ maxn ];LINE line[ maxm ];double mat[ maxn ][ maxn ];double dist( POINT a,POINT b ){double sum = (a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y);return sqrt( sum );} double xmult( POINT a,POINT b,POINT c ){ return ( a.x-c.x )*( b.y-c.y )-( a.y-c.y )*( b.x-c.x ); } bool inLine( LINE now,POINT p ){ double minx,maxx,miny,maxy; minx=min( now.x1,now.x2 ); maxx=max( now.x1,now.x2 ); miny=min( now.y1,now.y2 ); maxy=max( now.y1,now.y2 ); if( p.x>=minx&&p.x<=maxx&&p.y>=miny&&p.y<=maxy ) return true; else return false; } bool Intersection( LINE one,LINE two ){ double d1,d2,d3,d4; POINT t1,t2,t3,t4; t1.x = one.x1,t1.y = one.y1,t2.x = one.x2,t2.y = one.y2; t3.x = two.x1,t3.y = two.y1,t4.x = two.x2,t4.y = two.y2; d1=xmult( t3,t2,t1 ); d2=xmult( t4,t2,t1 ); d3=xmult( t1,t3,t4 ); d4=xmult( t2,t3,t4 ); if( d1*d2<0&&d3*d4<0 ) return true;//相互跨过 if( d1==0&&inLine( one,t3 )==true ) return true; if( d2==0&&inLine( one,t4 )==true ) return true; if( d3==0&&inLine( two,t1 )==true ) return true; if( d4==0&&inLine( two,t2 )==true ) return true;//分别表示某个点在一条直线上的情况 return false; }void init(){cnt_line = cnt_point = 0;for( int i=0;i<maxn;i++ ){for( int j=0;j<maxn;j++ ){mat[ i ][ j ] = inf;}}}//initvoid addline( double x1,double y1,double x2,double y2 ){line[ cnt_line ].x1=x1,line[ cnt_line ].y1=y1;line[ cnt_line ].x2=x2,line[ cnt_line ].y2=y2;cnt_line++;}void addpoint( double x,double y ){point[ cnt_point ].x = x;point[ cnt_point ].y = y;cnt_point++;}bool test( POINT a,POINT b ){LINE tt;tt.x1 = a.x,tt.y1 = a.y;tt.x2 = b.x,tt.y2 = b.y;//printf("a.flag:%d b.flag:%d\n",a.f,b.f);for( int i=0;i<cnt_line;i++ ){if( a.f!=line[ i ].f && b.f!=line[ i ].f && Intersection( tt,line[ i ] )==1 )return false;}return true;}double dij( int s,int t ){int vis[ maxn ];double dis[ maxn ];for( int i=0;i<cnt_point;i++ ){dis[ i ] = mat[ s ][ i ];vis[ i ] = 0;}dis[ s ] = 0;vis[ s ] = 1;//double sum = 0;for( int i=0;i<cnt_point;i++ ){int k;double tmax;k =-1,tmax = inf;for( int j=0;j<cnt_point;j++ ){if( vis[ j ]==0&&tmax>dis[ j ] ){tmax = dis[ j ];k=j;}}if( k==-1 ) break;vis[ k ] = 1;//sum += tmax;for( int j=0;j<cnt_point;j++ ){if( vis[ j ]==0&&dis[ j ]>dis[ k ]+mat[ k ][ j ] ){dis[ j ] = dis[ k ]+mat[ k ][ j ];}}}return dis[ t ];}int main(){int m;while( scanf("%d",&m),m!=-1 ){init();S.x = 0.0,S.y = 5.0;T.x = 10.0,T.y = 5.0;if( m==0 ){printf("%.2lf\n",dist( S,T ));continue;}int flag = 0;point[ cnt_point ].f = flag++;addpoint( S.x,S.y );point[ cnt_point ].f = flag++;addpoint( T.x,T.y );//start and end double x,y1,y2,y3,y4;for( int num=1;num<=m;num++ ){scanf("%lf%lf%lf%lf%lf",&x,&y1,&y2,&y3,&y4);line[ cnt_line ].f = flag;addline( x,0.0,x,y1 );line[ cnt_line ].f = flag;addline( x,y2,x,y3 );line[ cnt_line ].f = flag;addline( x,y4,x,10.0 );//这三条线段归为一类point[ cnt_point ].f = flag;addpoint( x,y1 );point[ cnt_point ].f = flag;addpoint( x,y2 );point[ cnt_point ].f = flag;addpoint( x,y3 );point[ cnt_point ].f = flag;addpoint( x,y4 );//这四个点归为一类flag++;}//printf("flag:%d\ncnt_point:%d\ncnt_line:%d\n",flag,cnt_point,cnt_line);for( int i=0;i<cnt_point;i++ ){for( int j=i+1;j<cnt_point;j++ ){if( point[ i ].f!=point[ j ].f&&test( point[ i ],point[ j ] )==true ){mat[ i ][ j ] = mat[ j ][ i ] = dist( point[ i ],point[ j ] );//printf("mat[ %d ][ %d ] = %.2lf\n",i,j,mat[i][j]);}}}if( mat[ 0 ][ 1 ]!=inf ){printf("%.2lf\n",mat[ 0 ][ 1 ]);continue;}double ans = dij( 0,1 );printf("%.2lf\n",ans);}return 0;}
