#include <bits/stdc++.h>

using namespace std;

int main(){
    double a, b, c, d, e, f;
    cin >> a >> b >> c >> d >> e >> f;
    f -= e;
    c /= a, d /= a, f /= a;
    f += (c * c + d * d) / 4;
    cout << setprecision(15) << sqrt(f) << endl;
    
    return 0;
}