#include <fstream>
#define INF 2000000001
using namespace std;
ifstream f("energii.in");
ofstream g("energii.out");
int n,gmax,i,x,y,j,a[1011];
int main()
{
    f>>n;
    f>>gmax;
    for(i=1;i<=gmax;i++)
        a[i]=INF;
    for(i=1;i<=n;i++)
    {
        f>>x>>y;
        for(j=gmax-x;j>=0;j--)
            a[j+x]=min(a[j+x],a[j]+y);
    }
    if(a[gmax]==INF)
        g<<-1;
    else
        g<<a[gmax]<<'\n';
    return 0;
}