using namespace std;
#define nmax 1002
#define inf 32000
#define wmax 15002
#include<cstdio>
 long  v[nmax],c[nmax],n,j;
 long cmin[15003], w,i;

void read()
{
	freopen("energii.in","r",stdin);
	scanf("%li%li",&n,&w); 
	for(i=1;i<=n;i++)
		scanf("%li%li",&v[i],&c[i]);
	
}

void solve()
{
	for(i=1;i<=wmax;i++) cmin[i]=inf;
	for(j=1;j<=n;j++)
		for(i=w-1;i>=0;i--)
			if(cmin[i+v[j]] > cmin[i]+c[j] )
				cmin[i+v[j]]=cmin[i]+c[j];
}

void afis()
{
	 long min=inf;
	freopen("energii.out","w",stdout);
	for(i=w;i<=wmax;i++)
		if(cmin[i]<min) min=cmin[i];
	if(min!=inf)
	printf("%li\n",min);
	else printf("-1\n");
}

int main()
{
	read();
	solve();
	afis();
	return 0;
}