#include #include #include #include #include #include #include #include #include const long long INF = 1e6+7; const long long MOD = 1e9+7; const double PI=acos(-1); using namespace std; int main(){ double n; cin >> n; double r2=n/PI; double r=sqrt(r2); cout << fixed << setprecision(10) << r << endl; return 0; }