#include <iostream>
using namespace std;
int main()
{
float f, a, b;
double p=1.5;
int c;
cin>>a;
if(a>=0)
{
c=a/p;
b=a/p;
a=(b-c)*p;
f=a*a*a-2.25*a;
}
else if(a<0)
{
c=(-a)/p;
a=(c+1)*p+a;
f=a*a*a-2.25*a;
}
cout<<f<<endl;
return 0;
}
I2luY2x1ZGUgPGlvc3RyZWFtPgp1c2luZyBuYW1lc3BhY2Ugc3RkOwppbnQgbWFpbigpIAp7CglmbG9hdCBmLCBhLCBiOwoJZG91YmxlIHA9MS41OwoJaW50IGM7CgljaW4+PmE7CgoJaWYoYT49MCkKCXsKCQljPWEvcDsKCQliPWEvcDsKCQlhPShiLWMpKnA7CgkJZj1hKmEqYS0yLjI1KmE7Cgl9CgllbHNlIGlmKGE8MCkKCXsKCQljPSgtYSkvcDsKCQlhPShjKzEpKnArYTsKCQlmPWEqYSphLTIuMjUqYTsKCX0KCWNvdXQ8PGY8PGVuZGw7CglyZXR1cm4gMDsKfQ==