Overview

For each type of card, compare the required number of cards with the current number of cards to find how many are missing. If you already have at least the required number, output \(0\).

Analysis

For the \(i\)-th type of card, \(A_i\) cards are required, and you currently have \(B_i\) cards.

• If \(A_i > B_i\), you need to buy the missing \(A_i - B_i\) cards.
• If \(A_i \leq B_i\), you already have enough cards, so the number of cards to buy is \(0\).

For example, if \(5\) cards are required and you currently have \(2\), you need \(3\) more cards. On the other hand, if \(5\) cards are required and you currently have \(7\), you do not need to buy any.

If you simply output \(A_i - B_i\), it will produce a negative value when you have extra cards, resulting in a wrong answer. Therefore, we take the maximum of \(0\) and \(A_i - B_i\).

In other words, the answer can be obtained with the following formula:

\(\max(0, A_i - B_i)\)

Since each card type can be computed independently, no complex processing or optimization is needed.

Algorithm

1. Read the number of card types, \(N\).
2. Repeat the following process \(N\) times:
   • Read the required number \(A\) and the current number \(B\).
   • Compute \(\max(0, A - B)\) and output it.

By processing the inputs as they are read, the answer for each card type can be printed in the required order.

Complexity

• Time complexity: \(O(N)\)
  For each type, subtraction and comparison are performed once.
• Space complexity: \(O(1)\)
  Since the input can be processed line by line, there is no need to store it in an array or list.

Implementation Notes

• Using max(0, A - B) in Python allows you to handle cases where the missing count would be negative concisely.

• This formula correctly outputs \(0\) even when \(A = B\).

• Since the answer for each card type should be output on a separate line, call print inside the loop.

  Source Code

import sys

input = sys.stdin.buffer.readline

N = int(input())
for _ in range(N):
    A, B = map(int, input().split())
    print(max(0, A - B))

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This editorial was generated by gpt-6-astra-medium.