AtCoder Beginner Contest 153
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Problem Statement
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Ibis is fighting with a monster.
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The health of the monster is $H$.
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Ibis can cast $N$ kinds of spells. Casting the $i$-th spell decreases the monster's health by $A_i$, at the cost of $B_i$ Magic Points.
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The same spell can be cast multiple times. There is no way other than spells to decrease the monster's health.
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Ibis wins when the health of the monster becomes $0$ or below.
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Find the minimum total Magic Points that have to be consumed before winning.
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Constraints
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$1 \leq H \leq 10^4$$1 \leq N \leq 10^3$$1 \leq A_i \leq 10^4$$1 \leq B_i \leq 10^4$- All values in input are integers.
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Input
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Input is given from Standard Input in the following format:
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H N
A_1 B_1
:
A_N B_N翻译中…
Output
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Print the minimum total Magic Points that have to be consumed before winning.
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样例
Input #1
9 3
8 3
4 2
2 1
Output #1
4
First, let us cast the first spell to decrease the monster's health by $8$, at the cost of $3$ Magic Points. The monster's health is now $1$.
Then, cast the third spell to decrease the monster's health by $2$, at the cost of $1$ Magic Point. The monster's health is now $-1$.
In this way, we can win at the total cost of $4$ Magic Points.
Input #2
100 6
1 1
2 3
3 9
4 27
5 81
6 243
Output #2
100
It is optimal to cast the first spell $100$ times.
Input #3
9999 10
540 7550
691 9680
700 9790
510 7150
415 5818
551 7712
587 8227
619 8671
588 8228
176 2461
Output #3
139815
题目信息
题面与样例版权归 AtCoder 及出题人所有；中文翻译由 AI 生成（CI 管线），如有出入请以原文为准。