#include <iostream>
#include <algorithm>
#include <cmath>
#include <cstdlib>
#include <vector>
#include <queue>
#include <utility>
using namespace std;

typedef pair<int, int> P;
typedef long long ll;

#define For(i, a, b) for(int i = (a); i < (b); i++)
#define Rep(i, n) For(i, 0, (n))

const double inf = 1e15;
const int mod = 1000000007;

double dp[1 << 15][20];
int x[20], y[20]; double w[20]; double all_w;
int dis[20][20];

int main(){
	int a, b; cin >> a >> b;
	int n; cin >> n;
	x[0] = a; y[0] = b;
	For(i, 1, n + 1){
		cin >> x[i] >> y[i] >> w[i];
		all_w += w[i];
	}
	n += 1;
	Rep(i, 1 << n) Rep(j, n) dp[i][j] = inf;
	dp[0][0] = 0;
	Rep(i, 1 << n) Rep(j, n) if(dp[i][j] < inf){
		double now_w = all_w;
		Rep(k, n) if(i & 1 << k) now_w -= w[k];
		Rep(k, n) if(!(i & 1 << k)){
			double dis = abs(x[j] - x[k]) + abs(y[j] - y[k]);
			double add_dis = dis * (now_w + 100.0) / 120;
			dp[i | 1 << k][k] = min(dp[i | 1 << k][k], dp[i][j] + add_dis + w[k]);
		}
	}
	printf("%.9f\n", dp[(1 << n) - 1][0]);
	return 0;
}