# http://c...content-available-to-author-only...e.com/q/78141/34718
x=input()
i=1;k=0
while i*i<x:k+=i*i;i+=2
print k
f=lambda x:sum((n-~n)**2for n in range(x)if(n-~n)**2<x)
#print f(10000)
IyBodHRwOi8vYy4uLmNvbnRlbnQtYXZhaWxhYmxlLXRvLWF1dGhvci1vbmx5Li4uZS5jb20vcS83ODE0MS8zNDcxOAoKeD1pbnB1dCgpCmk9MTtrPTAKd2hpbGUgaSppPHg6ays9aSppO2krPTIKcHJpbnQgawoKZj1sYW1iZGEgeDpzdW0oKG4tfm4pKioyZm9yIG4gaW4gcmFuZ2UoeClpZihuLX5uKSoqMjx4KQojcHJpbnQgZigxMDAwMCk=