#include<bits/stdc++.h>
using namespace std;
int n,m;
struct node{
	int w,v;
	double t;
}a[30005];
bool cmp(node x,node y){
	if(x.t!=y.t)return x.t>y.t;
	else return x.w>y.w;
}
int main(){
	freopen("delicious.in","r",stdin);
	freopen("delicious.out","w",stdout);
	cin>>n>>m;
	for(int i=1;i<=n;++i){
		cin>>a[i].w>>a[i].v;
		a[i].t=(double)a[i].v/(double)a[i].w;
	}
	sort(a+1,a+n+1,cmp);
	int ans=0;
	for(int i=1;i<=n;++i){
		if(m>=a[i].w){
			ans+=a[i].v;
			m-=a[i].w;
		}
	}
	cout<<ans;
	return 0;
}