#include<fstream>
#include<algorithm>

using namespace std;

ifstream fi("f.in");
ofstream fo("f.out");

struct rucsac{
				int greutate,cost;
				};
				
int N,G,K;
rucsac R[10001];

bool comp(rucsac a,rucsac b){
return a.cost>b.cost;	
}

int main()
{
	fi>>N>>G;
	for(int i=1;i<=N;i++) fi>>R[i].greutate>>R[i].cost;
	sort(R+1,R+1+N,comp);
	for(int i=1;i<=N;i++){
							if(G-R[i].greutate>=0) {
													K+=R[i].cost;
													G-=R[i].greutate;
													}
							}
	fo<<K;
}