import java.util.*;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    double x0 = sc.nextDouble();
    double y0 = sc.nextDouble();
    int n = sc.nextInt();
    double[] x = new double[n + 1];
    double[] y = new double[n + 1];
    double[] w = new double[n + 1];
    for(int i = 1; i < n + 1; i++) {
      x[i] = sc.nextDouble();
      y[i] = sc.nextDouble();
      w[i] = sc.nextDouble();
    }
    int p = (int)Math.pow(2, n);
    double[][] dp = new double[p][n + 1];

    for(int i = 0; i < p; i++) {
      for(int j = 0; j < n + 1; j++) {
        dp[i][j] = 1000000000;
      }
    }

    dp[0][0] = 0;

    double[] s = new double[p];

    for(int i = 1; i < p; i++) {
      for(int j = 0; j < n; j++) {
        if((i & (1 << j)) != 0) s[i] += w[j];
      } 
    }

    double sum = s[p - 1];

    for(int i = 1; i < p; i++) {
      for(int j = 0; j < n; j++) {
        if((i & (1 << j)) != 0) {
          int i1 = i - (1 << j);
          for(int k = 1; k < n + 1; k++) {
            if(dp[i1][k] != 1000000000) {
              double t = dp[i1][k];
              t = (t + (((double)Math.abs(x[k] - x[j]) + (double)Math.abs(y[k] - y[j])) * (double)(sum - s[i1] + 100)) / (double)(120));
              dp[i][j] = Math.min(dp[i][j], t);
            }
          }
        }
      }
    }

    double ans = 1000000000;

    for(int j = 1; j < n + 1; j++) {
      double t = dp[p - 1][j];
      t = (t + (((double)Math.abs(x0 - x[j]) + (double)Math.abs(y0 - y[j])) * (double)100) / (double)(120));
      ans = Math.min(ans, t);
    }
    System.out.println(ans);
  }
}