102292: [AtCoder]ABC229 C - Cheese

Problem Statement

Takahashi, who works for a pizza restaurant, is making a delicious cheese pizza for staff meals.
There are $N$ kinds of cheese in front of him.
The deliciousness of the $i$-th kind of cheese is $A_i$ per gram, and $B_i$ grams of this cheese are available.
The deliciousness of the pizza will be the total deliciousness of cheese he puts on top of the pizza.
However, using too much cheese would make his boss angry, so the pizza can have at most $W$ grams of cheese on top of it.
Under this condition, find the maximum possible deliciousness of the pizza.

Constraints

• All values in input are integers.
• $1 \le N \le 3 \times 10^5$
• $1 \le W \le 3 \times 10^8$
• $1 \le A_i \le 10^9$
• $1 \le B_i \le 1000$

Input

Input is given from Standard Input in the following format:

$N$ $W$
$A_1$ $B_1$
$A_2$ $B_2$
$\vdots$
$A_N$ $B_N$

Output

Print the answer as an integer.

Sample Input 1

3 5
3 1
4 2
2 3

Sample Output 1

15

The optimal choice is to use $1$ gram of cheese of the first kind, $2$ grams of the second kind, and $2$ grams of the third kind.
The pizza will have a deliciousness of $15$.

Sample Input 2

4 100
6 2
1 5
3 9
8 7

Sample Output 2

100

There may be less than $W$ grams of cheese in total.

Sample Input 3

10 3141
314944731 649
140276783 228
578012421 809
878510647 519
925326537 943
337666726 611
879137070 306
87808915 39
756059990 244
228622672 291

Sample Output 3

2357689932073

问题描述

在披萨店工作的高桥正在为员工餐制作美味的奶酪披萨。

他面前有$N$种奶酪。

第$i$种奶酪每克的美味度是$A_i$，这种奶酪有$B_i$克可用。

披萨的美味度将是放在披萨上面的奶酪的总美味度。

但是，使用太多的奶酪会让他的老板生气，所以披萨上面最多只能有$W$克奶酪。

在这种条件下，找出披萨的最大可能美味度。

约束条件

• 输入中的所有值都是整数。
• $1 \le N \le 3 \times 10^5$
• $1 \le W \le 3 \times 10^8$
• $1 \le A_i \le 10^9$
• $1 \le B_i \le 1000$

输入

从标准输入以以下格式获取输入：

$N$ $W$
$A_1$ $B_1$
$A_2$ $B_2$
$\vdots$
$A_N$ $B_N$

输出

将答案作为整数打印。

样例输入1

3 5
3 1
4 2
2 3

样例输出1

15

最佳选择是使用1克第一种奶酪，2克第二种奶酪，2克第三种奶酪。

披萨的美味度将是15。

样例输入2

4 100
6 2
1 5
3 9
8 7

样例输出2

100

奶酪的总重量可能少于$W$克。

样例输入3

10 3141
314944731 649
140276783 228
578012421 809
878510647 519
925326537 943
337666726 611
879137070 306
87808915 39
756059990 244
228622672 291

样例输出3

2357689932073