#include <iostream>
#include <cstdio>
#include <cmath>
#include <cstring>
using namespace std;
const double inf = 1e100, EPS = 1e-6;
const int W = 20;
double l, now;
int n;
struct wall
{
	double x, y[6], val[5];
} w[W];
// big bug:double->int
double length(double x1, double y1, double x2, double y2)
{
	double x = x1 - x2, y = y1 - y2;
	return sqrt(x * x + y * y);
}
double cross(double x1, double y1, double x2, double y2)
{
	return x1 * y2 - x2 * y1;
}
double same(double x0, double y0, double x3, double y3, double x1, double y1, double x2, double y2)
{
	double x = x3 - x0, y = y3 - y0; // y0->x0
	return cross(x, y, x1 - x0, y1 - y0) * cross(x, y, x2 - x0, y2 - y0);
}
// WA double 判断正负要用
int sign(double d)
{
	if (fabs(d) < EPS)
	{
		return 0;
	}
	else
		return d > 0 ? 1 : -1;
}
bool ob(int li, int lj, int ri, int rj)
{
	for (int i = li + 1; i < ri; i++)
	{
		for (int j = 0; j <= 4; j += 2)
		{
			//			printf("(%.0lf,%.0lf)(%.0lf,%.0lf)/(%.0lf,%.0lf)(%.0lf,%.0lf):",w[i].x,w[i].y[j],w[i].x,w[i].y[j+1],w[li].x,w[li].y[lj],w[ri].x,w[ri].y[rj]);
			//			printf("[%.2lf/%.2lf]\n",same(w[i].x,w[i].y[j],w[i].x,w[i].y[j+1],w[li].x,w[li].y[lj],w[ri].x,w[ri].y[rj]),same(w[li].x,w[li].y[lj],w[ri].x,w[ri].y[rj],w[i].x,w[i].y[j],w[i].x,w[i].y[j+1]));
			//两个都同方向才是，应该&&，错以为|| ,不是0都是真 两个小于0才是香蕉
			if (sign(same(w[i].x, w[i].y[j], w[i].x, w[i].y[j + 1], w[li].x, w[li].y[lj], w[ri].x, w[ri].y[rj])) < 0 && sign(same(w[li].x, w[li].y[lj], w[ri].x, w[ri].y[rj], w[i].x, w[i].y[j], w[i].x, w[i].y[j + 1])) < 0)
			{
				return 0;
			}
		}
	}
	return 1;
}
void find(int ii, int jj)
{
	for (int i = 0; i < ii; i++)
	{
		for (int j = 1; j <= 4; j++)
		{
			l = length(w[ii].x, w[ii].y[jj], w[i].x, w[i].y[j]);
			now = w[i].val[j] + l; // i j ii,jj搞反了
			if (now < w[ii].val[jj] && ob(i, j, ii, jj))
			{
				w[ii].val[jj] = now;
			}
			//			printf("(%.0lf,%.0lf)(%.0lf,%.0lf):length:%.3lf,now:%.3lf，val:%.3lf\n",w[ii].x,w[ii].y[jj],w[i].x,w[i].y[j],l,now,w[ii].val[jj]);
			if (i == 0)
				break;
		}
	}
}
void doit()
{
	for (int i = 1; i <= n; i++)
	{
		for (int j = 1; j <= 4; j++)
		{
			find(i, j);
			if (i == n)
				break;
		}
	}
}
int main()
{
	while (1)
	{
		scanf("%d", &n);
		if (n == -1)//-1return
			return 0;
		memset(&w, 0, sizeof(wall) * (n + 1));
		w[0].x = 0;
		w[0].y[1] = 5;
		w[0].val[1] = 0;
		for (int i = 1; i <= n; i++)
		{
			w[i].y[0] = 0;
			w[i].y[5] = 10;
			for (int j = 1; j <= 4; j++) //又打成i
			{
				w[i].val[j] = inf;
			}
		}
		for (int i = 1; i <= n; i++)
		{
			scanf("%lf", &w[i].x);
			//			cin>>w[i].x;
			for (int j = 1; j <= 4; j++) // 又是j
			{
				scanf("%lf", &w[i].y[j]);
				//				cin>>w[i].y[j];
			}
		}
		w[++n].x = 10;
		w[n].y[1] = 5;
		w[n].val[1] = inf; // bug 没赋值
		doit();
		printf("%.2lf\n", w[n].val[1]);
	}
	return 0;
}