According to the Bohr atomic model, the electrons of an atom move in a number of shells around the nucleus. Every shell has a different energy level and can contain a limited number of electrons. The electrons of a stable atom move in the shells with the least amount of energy.

Shells are represented by the letters K, L, M, N, O, P and Q, according to their increasing distance from the nucleus. The number is called shell number n. A shell with number n can contain a maximum of $$2n^2$$ electrons, as stated in the table below (this rule applies to $$n = 1$$ until $$n = 4$$, while $$n = 5, 6, 7$$ contain a maximum of 32 electrons):

shell K L M N O P Q
number $$(n)$$ 1 2 3 4 5 6 7
maximum occupation ($$\leq 2n^2$$) 2 8 18 32 32 32 32
cumulative occupation 2 10 28 60 92 124 156

Given the amount of electrons of an atom in stable condition. What is the outer filled shell? In a stable condition, the shells are filled from the inside to the outside. A sodium atom, for example, contains eleven electrons. In the stable condition, there are 2 electrons in the K-shell, 8 in the L-shell and the last electron is situated in the M-shell.


The amount of electrons $$e$$ in an atom, of which $$1 \leq e \leq 156$$.


The name of the outer shell if the atom is in a stable condition, described as follows: "The M-shell is the outer shell of a stable atom with 11 electrons.". The elements in italics should of course be filled in correctly on the basis of the data from the input.





The M-shell is the outer shell of a stable atom with 11 electrons.