#include <fstream>

#define NMAX 1005
#define INF 50000000
using namespace std;

ifstream in("energii.in");
ofstream out("energii.out");

int a[NMAX][NMAX] ;
int e[NMAX],c[NMAX];
int emin,n;
int i,j,w;

int main()
{
    in >> n >> emin;
    for(i=1; i<=n; i++)
    {
        in >> e[i] >> c[i];
    }

    for(i=0;i<=n;++i)
        for(w=1;w<=emin;++w)
                a[i][w] = INF;

    for( i=1;i<=n;i++)
        for(w=1;w<=emin;w++){
            a[i][w] = a[i-1][w];
            if(w >= e[i])
                a[i][w] = min(a[i][w],a[i-1][w-e[i]] + c[i]);
            else if(w <= e[i])
                a[i][w] = min(a[i][w],c[i]);
        }

    if(a[n][emin] == INF)
        out << "-1";
    else
        out << a[n][emin];
    in.close();
    out.close();
    return 0;
}