#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;
}
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