#include <vector>
#include <map>
#include <set>
#include <stack>
#include <queue>
#include <algorithm>
#include <utility>
#include <functional>
#include <sstream>
#include <iostream>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <ctime>
#include <climits>
#include <fstream>
using namespace std;
inline int toInt(string s) { int v; istringstream sin(s); sin >> v; return v;}
template<class T> inline string toStr(T x) { ostringstream sout; sout << x; return sout.str();}
typedef vector<int> vi;
typedef vector<vi>  vvi;
typedef vector<string> vs;
typedef pair<int, int> pii;
typedef long long ll;
#define ALL(a) (a).begin(),(a).end()
#define RALL(a) (a).rbegin(),(a).rend()
#define FOR(i,a,b) for(int i=(a);i<=(b);++i)
#define REP(i,n) FOR(i,0,(n)-1)
const double EPS = 1e-12;
const double PI = acos(-1.0);
const int INF = INT_MAX/10;

#define LT(x,y) ((x)-(y)<=-EPS)

#include <complex>
typedef complex<double> P;
typedef vector<P> vp;

double dot(P a, P b) {
	return (a.real()*b.real() + a.imag()*b.imag());
}

double cross(P a, P b) {
	return (a.real()*b.imag() - a.imag()*b.real());
}

vp cross_circles(P c1, double r1, P c2, double r2) {
	double d = abs(c2-c1);
	if(LT(r1+r2, d) || LT(d, fabs(r1-r2))) {
		return vp();
	}
	double l = 0.5*((r1*r1-r2*r2)/d+d);
	double h = sqrt(r1*r1-l*l);
	vp ret(2);
	ret[0] = P(l,+h)*(c2-c1)/d+c1;
	ret[1] = P(l,-h)*(c2-c1)/d+c1;
	return ret;
}

int is_point_on_ls(P a, P b, P c) {
	return (abs(a-c) + abs(c-b) < abs(a-b) + EPS);
}

int is_intersected_ls(P a1, P a2, P b1, P b2) { 
	if((cross(a2-a1, b1-a1) * cross(a2-a1, b2-a1) < -EPS) &&
	   (cross(b2-b1, a1-b1) * cross(b2-b1, a2-b1) < -EPS))
	   return true;
	return is_point_on_ls(a1, a2, b1) || is_point_on_ls(a1, a2, b2)
		|| is_point_on_ls(b1, b2, a1) || is_point_on_ls(b1, b2, a2);
}

typedef vector<double> vd;

struct state {
	int p;
	double c;
	state(int p, double c) : p(p), c(c) {};
	bool operator<(const state &o)const {
		return o.c<c;
	}
};

int main() {
	int n;
	while(cin >> n, n) {
		vector<vd> data(n, vd(3));
		REP(i, n) {
			REP(j, 3) {
				cin >> data[i][j];
			}
		}

		vp points(2*n);
		points[0] = P(data[0][0], data[0][1]);
		points[2*n-1] = P(data[n-1][0], data[n-1][1]);
		REP(i, n-1) {
			vp ccp = cross_circles(P(data[i][0], data[i][1]), data[i][2], P(data[i+1][0], data[i+1][1]), data[i+1][2]);
			points[2*i+1] = ccp[0];
			points[2*i+2] = ccp[1];
		}

		vector<vd> dist(2*n, vd(2*n, INF));
		REP(i, 2*n) {
			FOR(j, i+1, 2*n-1) {
				P s = points[i], g = points[j];
				int sl = (i+1)/2, gl = j/2;
				if(sl == 0) {
					sl++;
				}
				bool ok = true;
				FOR(k, sl, gl) {
					if(is_intersected_ls(s, g, points[2*k-1], points[2*k])) {

					} else {
						ok = false;
						break;
					}
				}
				if(ok) {
					dist[i][j] = dist[j][i] = abs(g-s);
				}
			}
		}

		vd cost(2*n, INF);
		cost[0] = 0;
		priority_queue<state> Q;
		Q.push(state(0, 0));
		while(!Q.empty()) {
			state st = Q.top();
			Q.pop();

			if(st.p == 2*n-1) {
				break;
			}

			REP(d, 2*n) {
				double nc = st.c + dist[st.p][d];
				if(nc < cost[d]) {
					cost[d] = nc;
					Q.push(state(d, nc));
				}
			}
		}

		printf("%.6f\n", cost[2*n-1]);
	}

	return 0;
}

Measured memory_bytes: 1532