1 #include <iostream>
 2 #include <queue>
 3 #include <stack>
 4 #include <cstdio>
 5 #include <vector>
 6 #include <map>
 7 #include <set>
 8 #include <bitset>
 9 #include <algorithm>
10 #include <cmath>
11 #include <cstring>
12 #include <cstdlib>
13 #include <string>
14 #include <sstream>
15 #include <time.h>
16 #define x first
17 #define y second
18 #define pb push_back
19 #define mp make_pair
20 #define lson l,m,rt*2
21 #define rson m+1,r,rt*2+1
22 #define mt(A,B) memset(A,B,sizeof(A))
23 #define mod 1000000007
24 using namespace std;
25 typedef long long LL;
26 const double PI = acos(-1);
27 const int N=2e5+10;
28 const int inf = 0x3f3f3f3f;
29 const LL INF=0x3f3f3f3f3f3f3f3fLL;
30 //已知圆锥的表面积S求最大的体积：V=S*sqrt(S/(72*PI))
31 int main()
32 {
33 #ifdef Local
34     freopen("data.txt","r",stdin);
35 #endif
36     double n;
37     cin>>n;
38     printf("%lf\n",n*sqrt(n/(72*PI)));
39 #ifdef Local
40     cerr << "time: " << (LL) clock() * 1000 / CLOCKS_PER_SEC << " ms" << endl;
41 #endif
42 }