#include <iostream>
#include <algorithm>
using namespace std;

class range {private: struct I{int x;int operator*(){return x;}bool operator!=(I& lhs){return x<lhs.x;}void operator++(){++x;}};I i,n;
public:range(int n):i({0}),n({n}){}range(int i,int n):i({i}),n({n}){}I& begin(){return i;}I& end(){return n;}};

struct point { int x, y; double w; };

const int inf = 987654321;
int n;
vector<point> ps;
vector<vector<double>> dp;

double calc_speed(int mask) {
  double weight = 0;
  for(int i : range(n)) {
    // 荷物がある = ビットが立っている
    if(mask>>i & 1) {
      weight += ps[i].w;
    }
  }
  return 120. / (weight + 100);
}

int dist(point p, point q) {
  return abs(p.x - q.x) + abs(p.y - q.y);
}

double rec(int mask, int v) {
  double &res = dp[v][mask];
  if(res != -1) { return res; }
  double speed = calc_speed(mask);
  // v番目から酒屋に帰る
  if(mask == 1) { return res = dist(ps[v], ps[0]) / speed; }
  res = inf;
  // v番目からi番目の配達先に行って荷物を降ろす
  for(int i : range(1, n)) {
    if(!(mask>>i & 1)) { continue; }
    int nmask = mask & ~(1<<i);
    res = min(res, rec(nmask, i) + dist(ps[v], ps[i]) / speed + ps[i].w);
  }
  return res;
}

int main(void) {
  int x0, y0; scanf("%d%d", &x0, &y0);
  scanf("%d", &n);
  n += 1;
  ps.resize(n);
  ps[0] = point({x0, y0, 0.});
  for(int i : range(1, n)) {
    int x, y; double w; scanf("%d%d%lf", &x, &y, &w);
    ps[i] = point({x, y, w});
  }
  dp.resize(n, vector<double>(1<<n, -1));
  double res = rec((1<<n)-1, 0);
  printf("%.9lf\n", res);
  return 0;
}