#include <fstream>

using namespace std;
	ifstream cin("energii.in");
	ofstream cout("energii.out");
	pair<int, int> v[1001]; /// energie, cost
	pair<int, int> suma[15001]; /// se-poate-Sau-nu, cost
int main()
{
	int g,w,pozmax;
	cin>>g>>w;
	for(int n2=1;n2<=g;n2++) {
		cin>>v[n2].first>>v[n2].second;
	}
	w*=2;
	if(v[1].first>w)
		pozmax=w;
	else
		pozmax=v[1].first;
	for(int n2=1;n2<=w;n2++) {
		suma[n2].second=10000001;
	}
	suma[v[1].first].first=1;
	suma[v[1].first].second=v[1].second;
	for(int n2=2;n2<=g;n2++) {
		suma[v[n2].first].first=1;
		suma[v[n2].first].second=min(suma[v[n2].first].second, v[n2].second);
		for(int n3=pozmax;n3>=0;n3--)
			if(suma[n3].first==1 && n3+v[n2].first<=w) {
				suma[n3+v[n2].first].first=1;
				suma[n3+v[n2].first].second=suma[n3].second+v[n2].second;
			}
		if(pozmax+v[n2].first>w)
			pozmax=w;
		else
			pozmax+=v[n2].first;
	}
	int s=suma[w].second;
	for(int n2=w/2;n2<=w;n2++)
		s=min(s,suma[n2].second);
	if(s==10000001)
		s=-1;
	cout<<s;
    return 0;
}