Problem:
Score : 500 points

Problem Statement

There are N boxes arranged in a circle. The i-th box contains A_i stones.

Determine whether it is possible to remove all the stones from the boxes by repeatedly performing the following operation:

Select one box. Let the box be the i-th box. Then, for each j from 1 through N, remove exactly j stones from the (i+j)-th box. Here, the (N+k)-th box is identified with the k-th box.

Note that the operation cannot be performed if there is a box that does not contain enough number of stones to be removed.

Constraints

1 ≦ N ≦ 10^5

1 ≦ A_i ≦ 10^9

Input

The input is given from Standard Input in the following format:

N
A_1 A_2 … A_N

Output

If it is possible to remove all the stones from the boxes, print YES. Otherwise, print NO.

Sample Input 1

5
4 5 1 2 3

Sample Output 1

YES

All the stones can be removed in one operation by selecting the second box.

Sample Input 2

5
6 9 12 10 8

Sample Output 2

YES

Sample Input 3

4
1 2 3 1

Sample Output 3

NO

Solution in Ruby (2.3.3) (judge verdict: Accepted)

n=gets.to_i
a=gets.split.map &:to_i
r=a.inject(:+)
j=true
t=n*(n+1)/2
j=false if r%t!=0
b=[a[0]-a[-1]]
(n-1).times do |i|
  b<< a[i+1]-a[i]
end
c=[]
n.times do |i|
  g=r/t-b[i]
  j=false if g%n!=0||g<0
  c<< g/n
end
puts j&&c.inject(:+)==r/t ? :YES : :NO