#include<stdio.h>
int i,j,v[6000],k,s,g,w,m[1005][3],ok,min;
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",&m[i][1],&m[i][2]);
	}
	v[0]=1;
	for(j=1;j<=g;j++)
	{
		for(i=5001;i>=0;i--)
		{
			if(v[i]>0)
			{
				v[i+m[j][1]]=v[i]+m[j][2];
				if(i==0)
					v[i+m[j][1]]--;
			}
		}
	}
	min=9999999;
	for(i=w;i<=5000;i++)
	{
		if(min>v[i]&&v[i]!=0)
		{
			min=v[i];
			ok=1;
		}
	}
	if(ok==0)
		printf("%d",-1);
	else
		printf("%d",min);
	return 0;
}