#include <fstream>
#include <algorithm>
#include <cmath>
using namespace std;
ifstream cin("energii.in");
ofstream cout("energii.out");
 
int a[1005], b[1005], c[5005], i, j,  n, p, s=0, g, w, mx;
 
 
int main()
{
	cin>>n>>w;
	mx=0;
	
	
	for (i=1; i<=n; ++i)
		cin>>a[i]>>b[i], mx=max(mx, a[i]);
		
	for (i=1; i<=n; ++i)
	{
		for (j=w; j>0; --j)
		{
		
			if (c[j])
				if (c[j+a[i]]==0 || c[j+a[i]]> c[j]+b[i] )
					c[j+a[i]]=c[j]+b[i];		
		}
		
		if (c[j+a[i]]==0 || c[j+a[i]]> c[j]+b[i] )
					c[j+a[i]]=c[j]+b[i];
		
	}
	
	int mn=100000000;
	
	for (i=w; i<=w+mx; ++i)
		if (c[i]) mn=min(mn, c[i]);
		
	if (mn==100000000) cout<<-1;
			else cout<<mn;
		
    return 0;
}