#include <bits/stdc++.h>

using namespace std;

const double EPS = 1e-8;
const double INF = 1e12;
typedef complex<double> P;
namespace std {
  bool operator < (const P& a, const P& b) {
    return real(a) != real(b) ? real(a) < real(b) : imag(a) < imag(b);
  }
}
double cross(const P& a, const P& b) {
  return imag(conj(a)*b);
}
double dot(const P& a, const P& b) {
  return real(conj(a)*b);
}

struct L : public vector<P> {
  L(const P &a, const P &b) {
    push_back(a); push_back(b);
  }
  L(pair<P, P> pp) {
    push_back(pp.first); push_back(pp.second);
  }
};

struct C {
  P p; double r;
  C(const P &p, double r) : p(p), r(r) { }
};

int ccw(P a, P b, P c) {
  b -= a; c -= a;
  if (cross(b, c) > 0)   return +1;       // counter clockwise
  if (cross(b, c) < 0)   return -1;       // clockwise
  if (dot(b, c) < 0)     return +2;       // c--a--b on line
  if (norm(b) < norm(c)) return -2;       // a--b--c on line
  return 0;
}

bool intersectLL(const L &l, const L &m) {
  return abs(cross(l[1]-l[0], m[1]-m[0])) > EPS || // non-parallel
         abs(cross(l[1]-l[0], m[0]-l[0])) < EPS;   // same line
}
bool intersectLS(const L &l, const L &s) {
  return cross(l[1]-l[0], s[0]-l[0])*       // s[0] is left of l
         cross(l[1]-l[0], s[1]-l[0]) < EPS; // s[1] is right of l
}
bool intersectLP(const L &l, const P &p) {
  return abs(cross(l[1]-p, l[0]-p)) < EPS;
}
bool intersectSS(const L &s, const L &t) {
  return ccw(s[0],s[1],t[0])*ccw(s[0],s[1],t[1]) <= 0 &&
         ccw(t[0],t[1],s[0])*ccw(t[0],t[1],s[1]) <= 0;
}
bool intersectSP(const L &s, const P &p) {
  return abs(s[0]-p)+abs(s[1]-p)-abs(s[1]-s[0]) < EPS; // triangle inequality
}

P projection(const L &l, const P &p) {
  double t = dot(p-l[0], l[0]-l[1]) / norm(l[0]-l[1]);
  return l[0] + t*(l[0]-l[1]);
}

double distanceLP(const L &l, const P &p) {
  return abs(p - projection(l, p));
}
double distanceLL(const L &l, const L &m) {
  return intersectLL(l, m) ? 0 : distanceLP(l, m[0]);
}
double distanceLS(const L &l, const L &s) {
  if (intersectLS(l, s)) return 0;
  return min(distanceLP(l, s[0]), distanceLP(l, s[1]));
}
double distanceSP(const L &s, const P &p) {
  const P r = projection(s, p);
  if (intersectSP(s, r)) return abs(r - p);
  return min(abs(s[0] - p), abs(s[1] - p));
}
double distanceSS(const L &s, const L &t) {
  if (intersectSS(s, t)) return 0;
  return min(min(distanceSP(s, t[0]), distanceSP(s, t[1])),
             min(distanceSP(t, s[0]), distanceSP(t, s[1])));
}
P crosspoint(const L &l, const L &m) {
  double A = cross(l[1] - l[0], m[1] - m[0]);
  double B = cross(l[1] - l[0], l[1] - m[0]);
  if (abs(A) < EPS && abs(B) < EPS) return m[0]; // same line
  if (abs(A) < EPS) assert(false); // !!!PRECONDITION NOT SATISFIED!!!
  return m[0] + B / A * (m[1] - m[0]);
}

pair<P, P> circle_circle_intersect(const C& c1, const C& c2) {
  P A = conj(c2.p-c1.p), B = (c2.r*c2.r-c1.r*c1.r-(c2.p-c1.p)*conj(c2.p-c1.p)), C = c1.r*c1.r*(c2.p-c1.p);
  P D = B*B-4.0*A*C;
  P z1 = (-B+sqrt(D))/(2.0*A)+c1.p, z2 = (-B-sqrt(D))/(2.0*A)+c1.p;
  return pair<P, P>(z1, z2);
}

struct Edge {
  int to;
  double cost;
};

vector<Edge> G[300];

map<P, int> mp;
int nidx;
void init_node_map(P ps, P pt, int N) {
  mp.clear();
  mp[ps] = 0;
  mp[pt] = (N-1)*2+1;
  nidx = 1;
}

int get_node(P p) {
  if(mp.find(p) == mp.end()) {
    mp[p] = nidx++;
  }
  return mp[p];
}

#define MAX (300)
double dist[MAX];

typedef pair<double, int> Pdi;
 
double dijkstra(int S, int T) {
  
  priority_queue<Pdi, vector<Pdi>, greater<Pdi> > PQ;
  fill(dist, dist+MAX, INF);
  dist[S] = 0;
  PQ.push(Pdi(0., S));
   
  while(!PQ.empty()) {
    Pdi pdi = PQ.top(); PQ.pop();
    const int u = pdi.second;
    for(int i=0; i<(int)G[u].size(); i++) {
      const Edge& e = G[u][i];
      if(dist[e.to] > dist[u]+e.cost) {
	dist[e.to] = dist[u]+e.cost;
	PQ.push(Pdi(dist[e.to], e.to));
      }
    }
  }
   
  return dist[T];
}

#define IINF2 (INT_MAX/2)

int main() {
  
  int N;
  while(cin >> N && N) {

    for(int i=0; i<300; i++) G[i].clear();

    vector<C> cs;
    for(int i=0; i<N; i++) {
      double x, y, r; cin >> x >> y >> r;
      cs.push_back(C(P(x, y), r));
    }
    
    vector<pair<P, P> > ips(N+1);
    ips[0].first = cs[0].p; // ips[0].second = P(-IINF2, -IINF2);
    for(int i=0; i<N-1; i++) {
      ips[i+1] = circle_circle_intersect(cs[i], cs[i+1]);
    }
    ips[N].first = cs[N-1].p; // ips.back().second = P(+IINF2, +IINF2);
    
    init_node_map(ips[0].first, ips[N].first, N);
    
    for(int i=0; i<N; i++) {
      for(int j=i+1; j<N+1; j++) {
	
	const int dij = j-i;
	
	for(int k=0; k<2; k++) {
	  
	  if(i == 0 && k == 1) continue;
	  
	  const P pti = k == 0 ? ips[i].first : ips[i].second;
	  const int a = get_node(pti);
	  
	  for(int l=0; l<2; l++) {
	    
	    if(j == N && l == 1) continue;
	    
	    const P ptj = l == 0 ? ips[j].first : ips[j].second;
	    const int b = get_node(ptj);
	    
	    bool ok = true;
	    const L sa(pti, ptj);
	    // 超えなければならない壁
	    for(int didx=1; didx<dij; didx++) {
	      const L sb(ips[i+didx]);
	      ok = ok && intersectSS(sa, sb);
	    }

	    
	    if(ok) {
	      const double len = abs(pti-ptj);
	      G[a].push_back((Edge){b, len});
	      G[b].push_back((Edge){a, len});
	    }
	    
	    
	  }
	}
      }
    }
    
    printf("%.6f\n", dijkstra(get_node(cs[0].p), get_node(cs[N-1].p)));
    
  }
  
  return 0;
}

Measured memory_bytes: 1512