### 题目描述

Bessie has gone to the mall’s jewelry store and spies a charm bracelet. Of course, she’d like to fill it with the best charms possible from the N (1 ≤ N ≤ 3,402) available charms. Each charm i in the supplied list has a weight Wi (1 ≤ Wi ≤ 400), a ‘desirability’ factor Di (1 ≤ Di ≤ 100), and can be used at most once. Bessie can only support a charm bracelet whose weight is no more than M (1 ≤ M ≤ 12,880).

Given that weight limit as a constraint and a list of the charms with their weights and desirability rating, deduce the maximum possible sum of ratings.

### 输入

* Line 1: Two space-separated integers: N and M
* Lines 2..N+1: Line i+1 describes charm i with two space-separated integers: Wi and Di

### 输出

* Line 1: A single integer that is the greatest sum of charm desirabilities that can be achieved given the weight constraints

4 6
1 4
2 6
3 12
2 7

23

### 提示

01背包问题，需要使用滚动数组进行优化，不然内存超限。

### 代码如下

``````#include<iostream>
#include<algorithm>
using namespace std;
int main()
{
int n,m,i,j;
int w[3500],p[3500];
while(cin>>n>>m)
{
int c[20000]={0};
for(i=1;i<=n;i++)
cin>>w[i]>>p[i];
for(i=1;i<=n;i++)
for(j=m;j>=w[i];j--)
c[j]=max(c[j],c[j-w[i]]+p[i]);
cout<<c[m]<<endl;
}
return 0;
}``````