Build Stairs

AtCoder

IDabc136_c

Time2000ms

Memory256MB

Difficulty—

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: $N$ $H_1$ $H_2$ $...$ $H_N$ [samples]

Samples

Input #1

5
1 2 1 1 3

Output #1

Yes

You can achieve the objective by decreasing the height of only the second square from the left by $1$.

Input #2

4
1 3 2 1

Output #2

No

Input #3

5
1 2 3 4 5

Output #3

Yes

Input #4

1
1000000000

Output #4

Yes

API Response (JSON)

{
  "problem": {
    "name": "Build Stairs",
    "description": {
      "content": "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: *   Dec",
      "description_type": "Markdown"
    },
    "platform": "AtCoder",
    "limit": {
      "time_limit": 2000,
      "memory_limit": 262144
    },
    "difficulty": "None",
    "is_remote": true,
    "is_sync": true,
    "sync_url": null,
    "sign": "abc136_c"
  },
  "statements": [
    {
      "statement_type": "Markdown",
      "content": "There are $N$ squares arranged in a row from left to right. The height of the $i$\\-th square from the left is $H_i$.\nFor each square, you will perform either of the following operations once:\n\n*   Dec...",
      "is_translate": false,
      "language": "English"
    }
  ]
}

Full JSON Raw Segments