#include <iostream>
#include <cmath>
#include <iomanip>
using namespace std;
int main() {
double x1, y1, z1, x, y, S;
cin >> x >> y;
cin >> x1 >> y1 >> z1;
S = sqrt((x1-x)*(x1-x) + (y1-y)*(y1-y) + z1*z1);
cout << fixed << setprecision(3) << 1/S;
return 0;
}
I2luY2x1ZGUgPGlvc3RyZWFtPgojaW5jbHVkZSA8Y21hdGg+CiNpbmNsdWRlIDxpb21hbmlwPgp1c2luZyBuYW1lc3BhY2Ugc3RkOwoKCmludCBtYWluKCkgewoJZG91YmxlIHgxLCB5MSwgejEsIHgsIHksIFM7CgljaW4gPj4geCA+PiB5OwoJY2luID4+IHgxID4+IHkxID4+IHoxOwoJUyA9IHNxcnQoKHgxLXgpKih4MS14KSArICh5MS15KSooeTEteSkgKyB6MSp6MSk7Cgljb3V0IDw8IGZpeGVkIDw8IHNldHByZWNpc2lvbigzKSA8PCAxL1M7CglyZXR1cm4gMDsKfQ==