#include <stdio.h>
#define INF 12128
char v[5128];
int main()
{
	int a,b,i,n,w,rez,j;
	freopen("energii.in","r",stdin);
	freopen("energii.out","w",stdout);
	scanf("%d%d", &n, &w);
	for(i=1;i<=w;i++)
		v[i]=INF;
	rez=INF;
	for(i=1;i<=n;i++)
	{
		scanf("%d%d", &a, &b);
		if(a>=w) {
			if(b<rez) rez=b; }
		else {
			for(j=w-a;j<=w;j++)
				if(v[j]+b<rez) rez=v[j]+b;
			for(j=w-a;j>=0;j--)
				if(v[j]+b<v[j+a]) v[j+a]=v[j]+b;
		}
	}
	if (rez!=INF) printf("%d\n",rez);
	else printf("-1\n");
}