#include<stdio.h>
#include<algorithm>
using namespace std;

int n,w,e[1003],c[1003],i,j,ma,rez=10000000,a[200000];

int main()
{
	freopen("energii.in","r",stdin);
	freopen("energii.out","w",stdout);
	
	scanf("%d%d",&n,&w);
	
	for(i=1;i<=n;++i)
		scanf("%d%d",&e[i],&c[i]);
	a[0]=1;
	
	int lim=0;
	for(i=1;i<=n;++i)
	{	for(j=lim;j>=0;--j) 
			if(a[j])
				if(!a[j+e[i]]||a[j+e[i]]>a[j]+c[i]) 
					{
						a[j+e[i]]=a[j]+c[i];
						if(j+e[i]>=w) rez=min(rez,a[j+e[i]]);
						lim=max(lim,j+e[i]);
					}
		lim=min(lim,w);
	}
	if(rez==10000000) printf("-1\n");
	else printf("%d\n",rez-1);

	fclose(stdin);
	fclose(stdout);
	
	return 0;
}