#include <fstream>
#include <algorithm>
#include <cmath>
using namespace std;
ifstream cin("energii.in");
ofstream cout("energii.out");
 
int a[1005], b[1005], c[500005], i, j,  n, p, s=0, g, w;
bool u[500005];
 
 
int main()
{
	cin>>n>>w;
	int mn=1000000000;
	for (i=1; i<=n; ++i)
		cin>>a[i]>>b[i];
		
	for (i=1; i<=20000; ++i) c[i]=mn;
		
	for (i=1; i<=n; ++i)
		for (j=w; j>=0; --j)		
					c[j+a[i]]=min((c[j]+b[i]), c[j+a[i]]);
		
	
	
	for (i=w; i<=20000; ++i)
		mn=min(mn, c[i]);
		
	if (mn==1000000000) cout<<-1;
			else cout<<mn;
		
    return 0;
}