program sample
	implicit none
    integer(8) :: i,j,k,l,m
    
    read(*,*) i
    
    if (mod(i,2)==0) then
    	write(*,*) (i/2)**2
    else
    	write(*,*) ((i+1)/2)*(i/2)
    end if
        
    
    
    
    stop
end program sample