import math


def calculate_tail_correction(cutoff, box_length, num_atoms):
    """
    Calculate the tail correction.
    
    Parameters
    ----------
    cutoff : float
        The curoff distance.
        
    box_length : float
        The length of the cell.
       
    num_atoms : int
        Number of atoms in a given system.
       
    Returns
    -------
    tail_co_LJ : float
        A float number that shows the value of tail correction energy for the given system.
    """
    
    tail_co_LJ = 0
    
    coeff = 0
    
    r3 = math.pow(1/cutoff,3)
    r9 = math.pow(r3,3)
    
    coeff = 8 * math.pi * (num_atoms ** 2)/(3 * (box_length ** 3))

    tail_co_LJ = coeff * (r9/3 - r3)
    
    return tail_co_LJ