#include
#include
#include

int main()
{
float y, s, x, eps;
int i;

freopen("input.txt", "r", stdin);
freopen("output.txt", "w", stdout);

scanf("%.2f\n%.5f", &x, &eps);

i = 1;
while (y >= eps)
{

y = x*x*x;
y /= (2*i - 1);
s +=y;
y *= (2*i - 1);
i++;
}
printf("%.5f", s);
return 0;
}