Lexicographical order is a very important concept in Competitive Programming. For using this concept, you first need to the the lexicographical order of the alphabet. The alphabet come in the following order:

• a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, u, v, w, x, y, z

I hope this blog has been useful for you.