# include <bits/stdc++.h>
using namespace std;
typedef long long ll;

const int N = 15;
ll n;
ll x[N], y[N];
double ans, w[N];
double dp[N][1 << N], W[1 << N];

double dis(ll i, ll j) {return abs(x[i] - x[j]) + abs(y[i] - y[j]);}

int main()
{
	scanf("%lld%lld%lld", &x[0], &y[0], &n);
	for (int i = 1; i <= n; i++) scanf("%lld%lld%lf", &x[i], &y[i], &w[i]);
	for (int S = 0; S < (1 << n); S++)
	{
		for (int i = 1; i <= n; i++)
		{
			if (!(S & (1 << (i - 1)))) W[S] += w[i];
			dp[i][S] = 1e18;
		}
	}
	for (int i = 1; i <= n; i++) dp[i][1 << (i - 1)] = dis(0, i) * (W[0] + 100.0) / 120.0 + w[i];
	for (int S = 1; S < (1 << n); S++)
	{
		for (int i = 1; i <= n; i++)
		{
			if (S & (1 << (i - 1)))
			{
				for (int j = 1; j <= n; j++)
				{
					if (i == j) continue;
					if (S & (1 << (j - 1)))
					{
						dp[i][S] = min(dp[i][S], dp[j][S ^ (1 << (i - 1))] + dis(i, j) * (W[S ^ (1 << (i - 1))] + 100.0) / 120.0 + w[i]);
					}
				}
			}
		}
	}
	ans = 1e18;
	for (int i = 1; i <= n; i++)
	{
		ans = min(ans, dp[i][(1 << n) - 1] + dis(i, 0) * 100.0 / 120.0);
	}
	printf("%.7f\n", ans);
	return 0;
}