#include <iostream>
#include <iomanip>
#include <cmath>
using namespace std;

int main() 
{
	int x1, y1;
	int x2, y2, z2;
	cin >> x1 >> y1;
	cin >> x2 >> y2 >> z2;
	double D = 1/sqrt((x2 - x1)*(x2 - x1) + (y2 - y1)*(y2 - y1) + z2*z2);
	cout << fixed << setprecision(3) << D << endl;
	return 0;
}