经典01背包问题
#include <iostream>
using namespace std;
const int N = 3e4+5;
int n, m;
int f[N];
int v, p;
int main()
{
cin >> n >> m;
for (int i = 1; i <= m; ++i)
{
cin >> v >> p;
for(int j=n; j>=v; j--)
f[j] = max(f[j], f[j-v]+v*p);
}
cout << f[n] << endl;
return 0;
}