#include <fstream>
using namespace std;
ifstream in("energii.in");
ofstream out("energii.out");
int maxi, n, i, j, m, e[1010], c[1010], a[15020];
int main(){
   in>>n>>m;
	
   for (i=1;i<=n;i++)
		in>>e[i]>>c[i];
	
	for (i=1;i<=15010;i++) a[i]=9999999;
   
	a[0]=0;
	
	for (i=1;i<=n;i++)
		for (j=m;j>=0;j--)
			if (a[j]!=-1&&a[j]+c[i]<a[j+e[i]]) a[j+e[i]]=a[j]+c[i];
	maxi=9999999;
	for (i=m;i<=15010;i++) 
		if (maxi>a[i]) maxi=a[i];
	
	if (maxi!=9999999)out<<maxi;
	else out<<-1;
	return 0;
}