#include <stdio.h>
#define INF 200000000
int main(){
	int x,y,i,n,w,a[7005],max,m,j;
	freopen("energii.in","r",stdin);
	freopen("energii.out","w",stdout);
	scanf("%d%d",&n,&w);
	for(i=1;i<=w;i++)
		a[i]=INF;
	m=INF;
	for(i=1;i<=n;i++){
		scanf("%d%d",&x,&y);
		if(x>=w) {
			if(y<m) m=y; }
		else {
			for(j=w-x;j<=w;j++)
				if(a[j]+y<m) m=a[j]+y;
			for(j=w-x;j>=0;j--)
				if(a[j]+y<a[j+x]) a[j+x]=a[j]+y;
		}
	}
	if (m!=INF) printf("%d",m);
	else printf("-1");
}