import std.stdio, std.range, std.conv, std.string, std.array, std.functional, std.math;
import std.algorithm.comparison, std.algorithm.iteration, std.algorithm.mutation, std.algorithm.searching, std.algorithm.setops, std.algorithm.sorting;
import std.container.binaryheap;
import std.typecons; 

void main()
{
    const input = readln().strip.to!(long);

    writeln(input/2 * (input/2 + input%2));
}