#include <fstream>
using namespace std;
ifstream fin("energii.in");
ofstream fout("energii.out");
int g,w,d[100010],e[5010],c[5010],i,j,minim;
int main() {
	fin>>g>>w;
	for (i=1;i<=g;i++)
		fin>>e[i]>>c[i];
	d[0]=1; minim=100000;
	for (i=1;i<=g;i++) {
		for (j=w;j>=0;j--) {
			if (d[j]!=0) {
				if (j+e[i]<w) {
					if (d[j+e[i]]==0)
						d[j+e[i]]=d[j]+c[i];
					else
						d[j+e[i]]=min(d[j+e[i]],d[j]+c[i]);
				}
				else
					minim=min(minim,d[j]+c[i]);
			}
		}
	}
	if (minim!=100000)
		fout<<minim-1;
	else
		fout<<-1;
	return 0;
}