2D Plane 2N Points

AtCoder

IDarc092_a

Time2000ms

Memory256MB

Difficulty—

On a two-dimensional plane, there are $N$ red points and $N$ blue points. The coordinates of the $i$\-th red point are $(a_i, b_i)$, and the coordinates of the $i$\-th blue point are $(c_i, d_i)$. A red point and a blue point can form a _friendly pair_ when, the $x$\-coordinate of the red point is smaller than that of the blue point, and the $y$\-coordinate of the red point is also smaller than that of the blue point. At most how many friendly pairs can you form? Note that a point cannot belong to multiple pairs. ## Constraints * All input values are integers. * $1 \leq N \leq 100$ * $0 \leq a_i, b_i, c_i, d_i < 2N$ * $a_1, a_2, ..., a_N, c_1, c_2, ..., c_N$ are all different. * $b_1, b_2, ..., b_N, d_1, d_2, ..., d_N$ are all different. ## Input Input is given from Standard Input in the following format: $N$ $a_1$ $b_1$ $a_2$ $b_2$ $:$ $a_N$ $b_N$ $c_1$ $d_1$ $c_2$ $d_2$ $:$ $c_N$ $d_N$ [samples]

Samples

Input #1

Output #1

2

For example, you can pair $(2, 0)$ and $(4, 2)$, then $(3, 1)$ and $(5, 5)$.

Input #2

Output #2

2

For example, you can pair $(0, 0)$ and $(2, 3)$, then $(1, 1)$ and $(3, 4)$.

Input #3

Output #3

0

It is possible that no pair can be formed.

Input #4

Output #4

Input #5

Output #5

API Response (JSON)

{
  "problem": {
    "name": "2D Plane 2N Points",
    "description": {
      "content": "On a two-dimensional plane, there are $N$ red points and $N$ blue points. The coordinates of the $i$\\-th red point are $(a_i, b_i)$, and the coordinates of the $i$\\-th blue point are $(c_i, d_i)$. A r",
      "description_type": "Markdown"
    },
    "platform": "AtCoder",
    "limit": {
      "time_limit": 2000,
      "memory_limit": 262144
    },
    "difficulty": "None",
    "is_remote": true,
    "is_sync": true,
    "sync_url": null,
    "sign": "arc092_a"
  },
  "statements": [
    {
      "statement_type": "Markdown",
      "content": "On a two-dimensional plane, there are $N$ red points and $N$ blue points. The coordinates of the $i$\\-th red point are $(a_i, b_i)$, and the coordinates of the $i$\\-th blue point are $(c_i, d_i)$.\nA r...",
      "is_translate": false,
      "language": "English"
    }
  ]
}

Full JSON Raw Segments