#include<fstream.h>   
ifstream f("energii.in");   
ofstream g("energii.out");   
const int Nmax=1010;   
const int Gmax=5010;   
int n,E,a[Nmax][Gmax],en,cost;   
int min(int x,int y)   
{   
 if(x<y)   
    return x;   
 return y;   
}

void init()
{
 for(int i=0;i<=n;i++)
    for(int j=0;j<=E;j++)
	a[i][j]=32000;
}

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

int main()
{
 citire();
 if(a[n][E]!=32000)
	 g<<a[n][E];
 else
	g<<-1;
 f.close();
 g.close();
 return 0;
}