content: package v012;
  import java.io.BufferedReader;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.InputStreamReader;
  import java.io.PrintWriter;
  import java.util.Arrays;
  import java.util.StringTokenizer;
  
  public class RobotChallenge_UVa1250 {
  
  	static Target[] targets;
  	static int N;
  	static double[][] memo;
  	
  	static double dp(int lst, int cur)
  	{
  		if(cur == N + 1)
  			return targets[lst].dist(targets[N + 1]) + 1;
  		if(memo[lst][cur] > -5)
  			return memo[lst][cur];
  		
  		double take = targets[cur].dist(targets[lst]) + 1 + dp(cur, cur + 1);
  		double leave = targets[cur].p + dp(lst, cur + 1);
  		return memo[lst][cur] = Math.min(take, leave);
  	}
  	
  	public static void main(String[] args) throws Exception 
  	{
  		Scanner sc = new Scanner(System.in);
  		PrintWriter out = new PrintWriter(System.out);
  	
  		while(true)
  		{
  			N = sc.nextInt();
  			if(N == 0)
  				break;
  			targets = new Target[N + 2];
  			targets[0] = new Target(0, 0, 0);
  			targets[N + 1] = new Target(100, 100, 0);
  			for(int i = 1; i <= N; ++i)
  				targets[i] = new Target(sc.nextInt(), sc.nextInt(), sc.nextInt());
  			
  			memo = new double[N + 1][N + 1];
  			for(int i = 0; i < N; ++i)
  				Arrays.fill(memo[i], -10);
  			out.printf("%.3f\n", dp(0, 1));
  		}
  		out.flush();
  		out.close();
  	}
  	
  	static class Target
  	{
  		int x, y, p;
  		
  		Target(int a, int b, int c) { x = a; y = b; p = c; } 
  		
  		double dist(Target t) { return Math.sqrt(sq(x - t.x) + sq(y - t.y)); }
  		
  		double sq(double x) { return x * x; }
  	}
  	
  	static class Scanner 
  	{
  		StringTokenizer st;
  		BufferedReader br;
  
  		public Scanner(InputStream s){	br = new BufferedReader(new InputStreamReader(s));}
  
  		public String next() throws IOException 
  		{
  			while (st == null || !st.hasMoreTokens()) 
  				st = new StringTokenizer(br.readLine());
  			return st.nextToken();
  		}
  
  		public int nextInt() throws IOException {return Integer.parseInt(next());}
  
  		public long nextLong() throws IOException {return Long.parseLong(next());}
  
  		public String nextLine() throws IOException {return br.readLine();}
  
  		public double nextDouble() throws IOException
  		{
  			String x = next();
  			StringBuilder sb = new StringBuilder("0");
  			double res = 0, f = 1;
  			boolean dec = false, neg = false;
  			int start = 0;
  			if(x.charAt(0) == '-')
  			{
  				neg = true;
  				start++;
  			}
  			for(int i = start; i < x.length(); i++)
  				if(x.charAt(i) == '.')
  				{
  					res = Long.parseLong(sb.toString());
  					sb = new StringBuilder("0");
  					dec = true;
  				}
  				else
  				{
  					sb.append(x.charAt(i));
  					if(dec)
  						f *= 10;
  				}
  			res += Long.parseLong(sb.toString()) / f;
  			return res * (neg?-1:1);
  		}
  
  		public boolean ready() throws IOException {return br.ready();}
  	}
  }