Andrey doesn't like sharp drops, especially in contests. Two numbers a and b form a sharp drop if ∣a−b∣>1. The competition is considered smooth if no difficulties of two neighboring problems form a sharp drop.
You are given 5 numbers — the complexity of the problems. Determine if these tasks form a smooth competition.
The first line contains five integers a, b, c, d, e (1≤a,b,c,d,e≤106) — problem complexity .
Print «YES
» if the numbers form a smooth competition, and «NO
» otherwise.
Explanation for the first example:
∣1−2∣=1, ∣2−2∣=0, ∣2−2∣=0, ∣2−1∣=1.
None of these pairs form a sharp drop, so the numbers 1,2,2,2,1 form a smooth contest.
Explanation for the second example: ∣1−2∣=1, ∣2−2∣=0, ∣2−1∣=1, ∣1−3∣=2.
As you can see, the last two numbers form a sharp drop, so the numbers 1,2,2,1,3 do not form a smooth contest.