#include<math.h>
#include<fstream>
#define MAXINT 32767
#define GMAX 5001
#define WMAX 1001
using namespace std;
ifstream f("energii.in");   
ofstream g("energii.out");   

int a[WMAX][GMAX],w,cost,n,E;  
 
void format()
{
 for(int i=0;i<=n;i++)
    for(int j=0;j<=E;j++)
	a[i][j]=MAXINT;
}

void ReadData()
{
    f>>n>>E;
    format();
    for(long i=1;i<=n;i++)
    {
	f>>w>>cost;
	for(int j=1;j<=E;j++)
	{
	    if(j<=w)
		a[i][j]=min(cost,a[i-1][j]);
	    else
		a[i][j]=min(a[i-1][j],a[i-1][j-w]+cost);
	}
    }
}

int main()
{
 ReadData();
 if(a[n][E]!=MAXINT) 
      g<<a[n][E];
 else 	
      g<<-1;
 f.close();
 g.close();
 return 0;
}