Prison

AtCoder

IDabc127_c

Time2000ms

Memory256MB

Difficulty—

We have $N$ ID cards, and there are $M$ gates. We can pass the $i$\-th gate if we have one of the following ID cards: the $L_i$\-th, $(L_i+1)$\-th, ..., and $R_i$\-th ID cards. How many of the ID cards allow us to pass all the gates alone? ## Constraints * All values in input are integers. * $1 \leq N \leq 10^5$ * $1 \leq M \leq 10^5$ * $1 \leq L_i \leq R_i \leq N$ ## Input Input is given from Standard Input in the following format: $N$ $M$ $L_1$ $R_1$ $L_2$ $R_2$ $\vdots$ $L_M$ $R_M$ [samples]

Samples

Input #1

4 2
1 3
2 4

Output #1

2

Two ID cards allow us to pass all the gates alone, as follows:

*   The first ID card does not allow us to pass the second gate.
*   The second ID card allows us to pass all the gates.
*   The third ID card allows us to pass all the gates.
*   The fourth ID card does not allow us to pass the first gate.

Input #2

Output #2

Input #3

100000 1
1 100000

Output #3

API Response (JSON)

{
  "problem": {
    "name": "Prison",
    "description": {
      "content": "We have $N$ ID cards, and there are $M$ gates. We can pass the $i$\\-th gate if we have one of the following ID cards: the $L_i$\\-th, $(L_i+1)$\\-th, ..., and $R_i$\\-th ID cards. How many of the ID card",
      "description_type": "Markdown"
    },
    "platform": "AtCoder",
    "limit": {
      "time_limit": 2000,
      "memory_limit": 262144
    },
    "difficulty": "None",
    "is_remote": true,
    "is_sync": true,
    "sync_url": null,
    "sign": "abc127_c"
  },
  "statements": [
    {
      "statement_type": "Markdown",
      "content": "We have $N$ ID cards, and there are $M$ gates.\nWe can pass the $i$\\-th gate if we have one of the following ID cards: the $L_i$\\-th, $(L_i+1)$\\-th, ..., and $R_i$\\-th ID cards.\nHow many of the ID card...",
      "is_translate": false,
      "language": "English"
    }
  ]
}

Full JSON Raw Segments