#include<stdio.h>
#define Nmax 101
#define Gmax 51
#define inf 11000
#define min(a,b) ((a<b) ? a : b)
int a[Nmax][Gmax],n,put;
void init()
{
 for(int i=0;i<=put;i++)
	a[0][i]=inf;
}

int program()
{
 int en,co,j,i;
 freopen("energii.in","r",stdin);
 scanf("%d%d",&n,&put);
 init();
 for(i=1;i<=n;i++)
 {	scanf("%d%d",&en,&co);
	for(j=1;j<=put;j++)
	{	if(j<=en)	a[i][j]=min(co,a[i-1][j]);
		else		a[i][j]=min(a[i-1][j],a[i-1][j-en]+co);
	}
 }
 fclose(stdin);
 if(a[n][put]==inf)
	return -1;
 else
	return a[n][put];
}

int main()
{
 freopen("energii.out","w",stdout);
 printf("%d\n",program());
 fclose(stdout);
 return 0;
}