题目描述
There are N squares arranged in a row from left to right. The height of the i-th square from the left is H_i.
For each square, you will perform either of the following operations once:
- Decrease the height of the square by 1.
- Do nothing.
Determine if it is possible to perform the operations so that the heights of the squares are non-decreasing from left to right.
-----Constraints-----
- All values in input are integers.
- $1 \leq N \leq 10^5$
- $1 \leq H_i \leq 10^9$
-----Input-----
Input is given from Standard Input in the following format:
N
H_1 H_2 ... H_N
-----Output-----
If it is possible to perform the operations so that the heights of the squares are non-decreasing from left to right, print Yes; otherwise, print No.
-----Sample Input-----
5
1 2 1 1 3
-----Sample Output-----
Yes
You can achieve the objective by decreasing the height of only the second square from the left by 1.
输入格式
见题面
输出格式
见题面