#include <complex>
#include <cstdio>
#include <string>
#include <queue>
#include <iostream>
#include <vector>
#include <tuple>
using namespace std;

#define loop(i,a,b) for(int i=(a);i<int(b);i++)
#define rep(i,b) loop(i,0,b)

typedef double R;

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

struct L : public vector<P> {
    L(const P &a = P(), const P &b = P()) {
        push_back(a); push_back(b);
    }
    // ax+by+c=0
    L(R a, R b, R c){
        if(fabs(a) < eps) *this = L(P(0,-c/b),P(1,-c/b));
        else if(fabs(b) < eps) *this = L(P(-c/a,0),P(-c/a,1));
        else *this = L(P(-c/a,0), P(0,-c/b));
    }
};

typedef vector<P> G;

struct C {
    P p; R r;
    C(const P &p, R r) : p(p), r(r) { }
    C(){}
};
bool debug = false;
struct VS {
    vector<string> ls;
    int cnt;
    double POINT_SIZE;
    double max_x, min_x, max_y, min_y;
    static char buf[2048];

    void chboundary(const C& c){
        max_x = max<double>(max_x, c.p.real() + c.r);
        max_y = max<double>(max_y, c.p.imag() + c.r);
        min_x = min<double>(min_x, c.p.real() - c.r);
        min_y = min<double>(min_y, c.p.imag() - c.r);
    }

    VS() : cnt(1), POINT_SIZE(1) { min_x = min_y = +inf; max_x = max_y = -inf; }
    VS& clear(){ return *this = VS(); }

    // 円
    VS& append(C const& c, const char* color = "black"){
        chboundary(c);
        sprintf(buf, "set object %d circle at %lf,%lf size %lf fc rgb \"%s\"",
                cnt++, (double)c.p.real(), (double)c.p.imag(), (double)c.r, color);
        ls.push_back(buf);
        return *this;
    }

    // 点
    VS& append(P const& p, const char* color = "black"){
        return append(C(p,POINT_SIZE), color);
    }

    // 多角形
    VS& append(G const& g, const char* color = "black"){
        string s;
        sprintf(buf, "set object %d polygon", cnt++);
        s += buf;
        rep(i,g.size()){
            chboundary(C(g[i],1));
            sprintf(buf, " %s %lf,%lf", i==0 ? "from" : "to",
                    (double)g[i].real(), (double)g[i].imag());
            s += buf;
        }
        sprintf(buf,
                " to %lf,%lf fc rgb \"%s\"",
                (double)g.front().real(), (double)g.front().imag(), color);
        s += buf; ls.push_back(s);
        return *this;
    }

    // 線分
    VS& append(L const& l, const char* color = "black"){
        return append(G{l[0],l[1]}, color);
    }

    // 直接入力
    VS& append(string const& s){
        ls.push_back(s); return *this;
    }

    // 出力
    VS& plot(string png_name = "plt.png"){
        if(!debug) return *this;
        FILE* fp = popen("gnuplot -persist", "w");
        // FILE* fp = stdout;
        // FILE* fp = fopen((png_name + ".plt").c_str(), "w");
        {
            double wy = max_y-min_y, wx = max_x-min_x;
            double d = abs(wy-wx);
            if(wy > wx){
                max_x += d/2; min_x -= d/2;
            } else {
                max_y += d/2; min_y -= d/2;
            }
            POINT_SIZE = 0.1;
        }
        fprintf(fp, "set size square\n");
        fprintf(fp, "set xrange [%lf:%lf]\n", min_x, max_x);
        fprintf(fp, "set yrange [%lf:%lf]\n", min_y, max_y);
        fprintf(fp, "set terminal pngcairo size 600,600\n");
        fprintf(fp, "set output \"%s\"\n", png_name.c_str());
        for(auto const& line : ls) fprintf(fp, "%s\n", line.c_str());
        fprintf(fp, "plot NaN notitle\n");
        fprintf(fp, "quit\n");
        pclose(fp);
        return *this;
    }
};
char VS::buf[2048];

VS vsualizer;

// CCW
int ccw(P a, P b, P c) {
    b -= a; c -= a;
    if (cross(b, c) > 0)   return +1; // a->b->c 反時計回り
    if (cross(b, c) < 0)   return -1; // a->b->c 時計回り
    if (dot(b, c) < 0)     return +2; // c--a--b 直線上
    if (norm(b) < norm(c)) return -2; // a--b--c 直線上
    return 0; // 2点以上が重なっている
}

// 交差判定
bool isiLL(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 isiLS(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 isiLP(const L &l, const P &p) {
    return abs(cross(l[1]-p, l[0]-p)) < eps;
}

bool isiSS(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 isiSP(const L &s, const P &p) {
    return abs(s[0]-p)+abs(s[1]-p)-abs(s[1]-s[0]) < eps; // triangle inequality
}

bool isiCP(const C &c, const P &p) {
    // 境界または内部
    return abs(c.p - p) <= c.r + eps;
}

int isiCC(const C& c1, const C& c2){
    double d = abs(c1.p - c2.p), r1 = c1.r, r2 = c2.r;
    if(abs(d - r1 - r2) < eps) return  1; // 接する
    if(d > r1 + r2)       return  0; // 共通部分を持たない
    if(d < r1 - r2)       return +3; // c1 が c2 の中にある
    if(d < r2 - r1)       return -3; // c2 が c1 の中にある
    return 2; // 2つの交点を持つ
}

// 射影
P proj(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]);
}

// 反射
P refl(const L &l, const P &p) {
    return p + 2. * (proj(l, p) - p);
}

// 距離
R dLP(const L &l, const P &p) {
    return abs(p - proj(l, p));
}

R dLL(const L &l, const L &m) {
    return isiLL(l, m) ? 0 : dLP(l, m[0]);
}

R dLS(const L &l, const L &s) {
    if (isiLS(l, s)) return 0;
    return min(dLP(l, s[0]), dLP(l, s[1]));
}

R dSP(const L &s, const P &p) {
    const P r = proj(s, p);
    if (isiSP(s, r)) return abs(r - p);
    return min(abs(s[0] - p), abs(s[1] - p));
}

R dSS(const L &s, const L &t) {
    if (isiSS(s, t)) return 0;
    return min(min(dSP(s, t[0]), dSP(s, t[1])),
               min(dSP(t, s[0]), dSP(t, s[1])));
}

R dCP(const C &c, const P &p) {
    return max(0. , abs(c.p - p));
}

// 交点
vector<P> iLL(const L &l, const L &m) {
    R A = cross(l[1] - l[0], m[1] - m[0]);
    R 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) throw "PRECONDITION NOT SATISFIED!!!";
    return {m[0] + B / A * (m[1] - m[0])};
}

vector<P> iSS(const L& s, const L& t) {
    if(isiSS(s,t)) return iLL(s,t);
    else return {};
}

vector<P> iLS(const L& l, const L& s){
    if(isiLS(l,s)) return iLL(l,s);
    else return {};
}

// !!! not verified !!!
vector<P> iCL(const C& c, const L& l){
    R d = dLP(l,c.p);
    // 接する
    if(abs(d-c.r) < eps) return { proj(l, c.p) };
    // 共有点を持たない
    if(d > c.r) return {};
    P h = proj(l, c.p);
    P v = h - c.p;
    P u = v * P(0,1) * sqrt(c.r*c.r - d*d) / abs(v);
    return {h+u, h-u};
}

// !!! not verified !!!
vector<P> iCC(const C& c1, const C& c2){
    int i = isiCC(c1,c2);
    // 共通部分なし || 内部
    if(i==0 || abs(i)==3) return {};
    R r1 = c1.r, r2 = c2.r, d = abs(c1.p - c2.p);
    // 接する
    if(i==1) return { c1.p + (c2.p - c1.p) * r1/d };
    // 2つの交点
    P p = c1.p - c2.p;
    R A = -2. * p.real(), B = -2. * p.imag();
    R C = norm(c1.p) - norm(c2.p) - r1*r1 + r2*r2;
    return iCL(c1, L(A,B,C));
}

int main(){
    int n;
    int cnt = 1;
    while(cin>>n && n){
        vsualizer.clear();
        vector<C> cs(n);
        rep(i,n){
            int x,y,r;
            cin>>x>>y>>r;
            cs[i] = C(P(x,y),r);
            vsualizer.append(cs[i], "red");
        }
        vector<L> ls(n-1);
        for(int i=0;i<n-1;i++){
            auto l = iCC(cs[i],cs[i+1]);
            ls[i] = L(l[0],l[1]);
        }

        int N=n*2;
        double d[N][N];
        rep(i,N)rep(j,N){
            if(i==j)d[i][j]=0;
            else d[i][j]=inf;
        }

        L st(cs[0].p,cs[n-1].p);
        bool okst = true;
        for(int i=0;i<n-1;i++){
            auto &ps = ls[i];
            P &p1=ps[0], &p2=ps[1];
            d[i*2][i*2+1] = abs(p1-p2);
            vsualizer.append(L(p1,p2));
            if(!isiSS(st,{p1,p2})) okst=false;
            for(int j=i+1;j<n-1;j++){
                auto &qs = ls[j];
                P &q1=qs[0], &q2=qs[1];
                L s11(p1,q1), s12(p1,q2), s21(p2,q1), s22(p2,q2);
                bool ok11 = true, ok12 = true, ok21 = true, ok22 = true;
                for(int k=i+1;k<=j-1;k++){
                    auto &rs = ls[k];
                    L s(rs[0],rs[1]);
                    if(!isiSS(s,s11))ok11=false;
                    if(!isiSS(s,s12))ok12=false;
                    if(!isiSS(s,s21))ok21=false;
                    if(!isiSS(s,s22))ok22=false;
                }
                if(ok11){
                    d[i*2][j*2] = d[j*2][i*2] = abs(p1-q1);
                    vsualizer.append(L(p1,q1));
                }
                if(ok12){
                    d[i*2][j*2+1] = d[j*2+1][i*2] = abs(p1-q2);
                    vsualizer.append(L(p1,q2));
                }
                if(ok21){
                    d[i*2+1][j*2] = d[j*2][i*2+1] = abs(p2-q1);
                    vsualizer.append(L(p2,q1));
                }
                if(ok22){
                    d[i*2+1][j*2+1] = d[j*2+1][i*2+1] = abs(p2-q2);
                    vsualizer.append(L(p2,q2));
                }
            }

            L s1(ps[0],cs[0].p);
            L s2(ps[1],cs[0].p);
            bool oks1 = true, oks2 = true;
            for(int j=0;j<i;j++){
                auto &t = ls[j];
                L s(t[0],t[1]);
                if(!isiSS(s,s1)) oks1 = false;
                if(!isiSS(s,s2)) oks2 = false;
            }
            if(oks1){
                d[N-1][i*2] = d[i*2][N-1] = abs(s1[0]-s1[1]);
                vsualizer.append(s1);
            }
            if(oks2){
                d[N-1][i*2+1] = d[i*2+1][N-1] = abs(s2[0]-s2[1]);
                vsualizer.append(s2);
            }
            L t1(ps[0],cs[n-1].p);
            L t2(ps[1],cs[n-1].p);
            bool okt1 = true, okt2 = true;
            for(int j=i+1;j<n-1;j++){
                auto t = ls[j];
                L s(t[0],t[1]);
                if(!isiSS(s,t1)) okt1 = false;
                if(!isiSS(s,t2)) okt2 = false;
            }
            if(okt1){
                d[N-2][i*2] = d[i*2][N-2] = abs(t1[0]-t1[1]);
                vsualizer.append(t1);
            }
            if(okt2){
                d[N-2][i*2+1] = d[i*2+1][N-2] = abs(t2[0]-t2[1]);
                vsualizer.append(t2);
            }
        }
        if(okst){
            d[N-1][N-2] = d[N-2][N-1] = abs(st[0]-st[1]);
            vsualizer.append(st);
        }
        rep(k,N)rep(i,N)rep(j,N)d[i][j] = min(d[i][j],d[i][k]+d[k][j]);
        printf("%.4lf\n",d[N-1][N-2]);

        string name = "pCase" + to_string(cnt++) + ".png";
        vsualizer.plot(name);
    }
}