Изи

Flat(X) = X + 5*n(x)

n(x) = 0, x in [2, 5]
n(x) = 1, x in [6, 10]
n(x) = 2, x in [11, 15]
n(x) = 3, x in [16, 20]
n(x) = 4, x in [21, 25]