package no134;

import java.util.Arrays;
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int[] x = new int[14];
		int[] y = new int[14];
		double[] w = new double[14];
		x[0] = sc.nextInt();
		y[0] = sc.nextInt();
		int n = sc.nextInt();
		for(int i=1;i<=n;i++) {
			x[i] = sc.nextInt();
			y[i] = sc.nextInt();
			w[i] = sc.nextDouble();
		}
		n++;
		int[][] d = new int[n][n];
		for(int i=0;i<n;i++) {
			for(int j=0;j<n;j++) {
				d[i][j] = Math.abs(x[i] - x[j]) + Math.abs(y[i] - y[j]);
			}
		}
		double[][] dp = new double[n][1<<n];
		for(int i=0;i<n;i++) {
			Arrays.fill(dp[i], 1E10);
		}
		dp[0][0] = 0;
		for(int s=0;s<1<<n;s++) {
			double t = 0;
			for(int i=0;i<n;i++) {
				if ((s >> i & 1) == 0) {
					t += w[i];
				}
			}
			t = (t + 100) / 120;
			for(int i=0;i<n;i++) {
				if (dp[i][s] >= 1E10) {
					continue;
				}
				for(int j=0;j<n;j++) {
					if (i == j || (s >> j & 1) == 1) {
						continue;
					}
//					System.out.println("(" + i + "," + Integer.toBinaryString(s) + ") -> (" + j + "," + Integer.toBinaryString(s | 1 << j) + ") : " + (dp[i][s] + d[i][j] * t));
					dp[j][s | 1 << j] = Math.min(dp[j][s | 1 << j], dp[i][s] + (d[i][j] * t + w[j]));
				}
			}
		}
		System.out.println(dp[0][(1<<n)-1]);
	}

}