log2(N)

AtCoder

IDabc215_b

Time2000ms

Memory256MB

Difficulty—

Given a positive integer $N$, find the maximum integer $k$ such that $2^k \le N$. ## Constraints * $N$ is an integer satisfying $1 \le N \le 10^{18}$. ## Input Input is given from Standard Input in the following format: $N$ [samples]

Samples

Input #1

Output #1

2

*   $k=2$ satisfies $2^2=4 \le 6$.
*   For every integer $k$ such that $k \ge 3$, $2^k > 6$ holds.

Therefore, the answer is $k=2$.

Input #2

Output #2

0

Note that $2^0=1$.

Input #3

1000000000000000000

Output #3

59

The input value may not fit into a $32$\-bit integer.

API Response (JSON)

{
  "problem": {
    "name": "log2(N)",
    "description": {
      "content": "Given a positive integer $N$, find the maximum integer $k$ such that $2^k \\le N$.",
      "description_type": "Markdown"
    },
    "platform": "AtCoder",
    "limit": {
      "time_limit": 2000,
      "memory_limit": 262144
    },
    "difficulty": "None",
    "is_remote": true,
    "is_sync": true,
    "sync_url": null,
    "sign": "abc215_b"
  },
  "statements": [
    {
      "statement_type": "Markdown",
      "content": "Given a positive integer $N$, find the maximum integer $k$ such that $2^k \\le N$.\n\n## Constraints\n\n*   $N$ is an integer satisfying $1 \\le N \\le 10^{18}$.\n\n## Input\n\nInput is given from Standard Input...",
      "is_translate": false,
      "language": "English"
    }
  ]
}

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