#include "bits/stdc++.h" using namespace std; #define all(x) begin(x),end(x) template ostream& operator<<(ostream &os, const pair &p) { return os << '(' << p.first << ", " << p.second << ')'; } template::value, typename T_container::value_type>::type> ostream& operator<<(ostream &os, const T_container &v) { string sep; for (const T &x : v) os << sep << x, sep = " "; return os; } #define debug(a) cerr << "(" << #a << ": " << a << ")\n"; typedef long long ll; typedef vector vi; typedef vector vvi; typedef pair pi; const int mxN = 1e5+1, oo = 1e9; int main() { ios_base::sync_with_stdio(false); cin.tie(NULL); double r,k; cin >> r >> k; double vol = r*r*acos(-1); for(int i=1;i=need) hi = mid; else lo = mid; } cout << lo << '\n'; } }