#include <bits/stdc++.h>

using namespace std;

#define FOR(i, a, b) for(int i = (a); i < (b); i++)
#define RFOR(i, a, b) for(int i = (a) - 1; i >= (b); i--)
#define SZ(a) int(a.size())
#define ALL(a) a.begin(), a.end()
#define PB push_back
#define MP make_pair
#define F first
#define S second

typedef long long LL;
typedef vector<int> VI;
typedef pair<int, int> PII;
typedef long double db;

db dis(db x1, db y1, db x2, db y2)
{
	db dx = x1 - x2;
	db dy = y1 - y2;
	return sqrt(dx * dx + dy * dy);
}

int main()
{
	ios::sync_with_stdio(0);
	cin.tie(0);
	
	int n;
	cin >> n;
	vector<db> x(n + 1), y(n + 1), t(n + 1);
	FOR (i, 0, n)
		cin >> x[i + 1] >> y[i + 1] >> t[i + 1];
	vector<db> d(n + 1);
	FOR (i, 0, n)
	{
		d[i + 1] = d[i] + dis(x[i], y[i], x[i + 1], y[i + 1]);
	}
	//FOR (i, 0, n + 1)
	//{
	//	cerr << i << ' ' << d[i] << ' ' << t[i] << '\n';
	//}
	//cerr << "\n\n\n";
	db ans = 1e47;
	int j = 0;
	FOR (i, 0, n + 1)
	{
		while (j < n + 1 && d[j] < d[i] + 100)
			j++;
		if (j == n + 1)
			break;
		db T = t[j - 1] - t[i];
		T += (100 - (d[j - 1] - d[i])) * (t[j] - t[j - 1]) / (d[j] - d[j - 1]);
		ans = min(ans, T);
	}
	j = n;
	RFOR (i, n + 1, 0)
	{
		while (j >= 0 && d[j] + 100 > d[i])
			j--;
		if (j == -1)
			break;
		db T = t[i] - t[j + 1];
		T += (100 - (d[i] - d[j + 1])) * (t[j + 1] - t[j]) / (d[j + 1] - d[j]); 
		ans = min(ans, T);
	}
	
	cout << fixed << setprecision(15) << ans << '\n';
	
	
	return 0;
}