#include <cstdio>

using namespace std;
int d[10000002];
int main()
{
    freopen("energii.in","r",stdin);
    freopen("energii.out","w",stdout);
    int n, gmax, g, p, i, j, dr, pmin;
    scanf("%d%d", &n, &gmax);
    for(i=1; i<=10000000; i++)
        d[i]=-1;
    dr=0;
    for(i=1; i<=n; i++)
    {
        scanf("%d%d", &g, &p);
        for(j=dr; j>=0; j--)
        {
                if (d[j]!=-1)
                {
                    if(d[j+g]==-1)
                        d[j+g]=p+d[j];
                    else
                    if (d[j+g]>d[j]+p)
                    {
                        d[j+g]=d[j]+p;


                    }
                    if (j+g>dr)
                        dr=j+g;

                }
            }
        }

    pmin=10000002;
    for(i=gmax; i<=dr; i++)
        if(pmin>d[i] && d[i]>0)
            pmin=d[i];
    if(pmin==10000002)
        pmin=-1;
    printf("%d\n", pmin);
    return 0;
}