Silver Fox vs Monster

AtCoder

IDabc153_f

Time2000ms

Memory256MB

Difficulty—

Silver Fox is fighting with $N$ monsters. The monsters are standing in a row, and we can assume them to be standing on a number line. The $i$\-th monster, standing at the coordinate $X_i$, has the _health_ of $H_i$. Silver Fox can use bombs to attack the monsters. Using a bomb at the coordinate $x$ decreases the healths of all monsters between the coordinates $x-D$ and $x+D$ (inclusive) by $A$. There is no way other than bombs to decrease the monster's health. Silver Fox wins when all the monsters' healths become $0$ or below. Find the minimum number of bombs needed to win. ## Constraints * $1 \leq N \leq 2 \times 10^5$ * $0 \leq D \leq 10^9$ * $1 \leq A \leq 10^9$ * $0 \leq X_i \leq 10^9$ * $1 \leq H_i \leq 10^9$ * $X_i$ are distinct. * All values in input are integers. ## Input Input is given from Standard Input in the following format: $N$ $D$ $A$ $X_1$ $H_1$ $:$ $X_N$ $H_N$ [samples]

Samples

Input #1

Output #1

2

First, let us use a bomb at the coordinate $4$ to decrease the first and second monsters' health by $2$.
Then, use a bomb at the coordinate $6$ to decrease the second and third monsters' health by $2$.
Now, all the monsters' healths are $0$. We cannot make all the monsters' health drop to $0$ or below with just one bomb.

Input #2

Output #2

5

We should use five bombs at the coordinate $5$.

Input #3

3 0 1
300000000 1000000000
100000000 1000000000
200000000 1000000000

Output #3

3000000000

Watch out for overflow.

API Response (JSON)

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    "name": "Silver Fox vs Monster",
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    "platform": "AtCoder",
    "limit": {
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      "memory_limit": 262144
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    "difficulty": "None",
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    "is_sync": true,
    "sync_url": null,
    "sign": "abc153_f"
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      "statement_type": "Markdown",
      "content": "Silver Fox is fighting with $N$ monsters.\nThe monsters are standing in a row, and we can assume them to be standing on a number line. The $i$\\-th monster, standing at the coordinate $X_i$, has the _he...",
      "is_translate": false,
      "language": "English"
    }
  ]
}

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