POJ 2392 Space Elevator

include<iostream>
#include<algorithm>
using namespace std;
struct node
{
int h,maxn,n;
};
node a[516];
int dp[516][40016];
bool is_greater(const node& a,const node& b)
{
return a.maxn<b.maxn;
}
int main()
{
int T;
int i,j,k;
cin>>T;
for(i=0;i<T;i++)
{
cin>>a[i].h>>a[i].maxn>>a[i].n;
}
sort(a,a+T,is_greater);
//多重背包
for(i=0;i<T;i++)
{
for(j=0;j<=a[i].maxn;j++)
{
for(k=0;k*a[i].h<=j && k<=a[i].n ;k++)
{
dp[i+1][j]=max(dp[i+1][j],dp[i][j-k*a[i].h]+k*a[i].h);
}
}
}
int result=-1;
for(i=1;i<=a[T-1].maxn;i++)
{
result=max(result,dp[T][i]);
}
cout<<result<<endl;
return 0;
}