#include<iostream>
using namespace std;
int main()
{
    int k,count_odd=0,count_even=0;
    cin>>k;
    for(int i=1;i<=k;i++)
    {
        if(i%2==0)
        {
            count_even++;
        }
        else if(i%2!=0)
        {
            count_odd++;
        }
    }
    cout << count_even*count_odd << endl;
    return 0;
}
