#include<iostream>
#include<fstream>
#include<algorithm>

    using namespace std;
    
int n, g, c, p;

pair <int, int> a[5001];
    
int main ()
{
	ifstream cin("rucsac.in");
	ofstream cout("rucsac.out");
	
	cin >> n >> g;
	
	for (int i = 1; i <= n; i++)
	{
		cin >> a[i].second;
		cin >> a[i].first;
		a[i].first = a[i].first * -1;
	}
	
	sort (a+1, a+n+1);
	
	for (int i = 1; i <= n; i++)
	{
		if (g - c >= a[i].second)
		{
			c += a[i].second;
			p += a[i].first * -1;			
		}
		else
			break;		    
	}
	cout << p;
	
}