#include<stdio.h>
int g,w,c[10001][10001],i,j;
struct energie{
	int e,pr;
}a[10001];
int main()
{
	freopen("energii.in","r",stdin);
	freopen("energii.out","w",stdout);
	scanf("%d%d",&g,&w);
	for(i=1;i<=g;i++)
		scanf("%d%d",&a[i].e,&a[i].pr);
	for(i=1;i<=g;i++)
		for(j=1;j<=w;j++)
			if(a[i].e<=j)
				if(a[i].pr+c[i-1][j-a[i].e]>c[i-1][j])
					c[i][j]=a[i].pr+c[i-1][j-a[i].e];
				else
					c[i][j]=c[i-1][j];
	i=g;j=w;
	if(c[i][j]>=w)
		printf("%d\n",c[i][j]);
	else
		printf("-1");
	return 0;
}