#include <cstdio>

using namespace std;
int d[10011005];
int main()
{
    freopen("energii.in","r",stdin);
    freopen("energii.out","w",stdout);
    int n,gmax,i,dr=0,g,p,j,min=2000000000;
    scanf("%d%d",&n,&gmax);
    for(i=1;i<=10011001;i++)
        d[i]=-1;
    for(i=1;i<=n;i++)
    {
        scanf("%d%d",&g,&p);
        for(j=dr;j>=0;j--)
        {
            if(d[j]!=-1)
            {
                if(j+g>=gmax)
                {
                    if(d[j]+p<min)
                    {
                        min=d[j]+p;
                        d[j+g]=min;
                    }
                }
                else
                {
                    if(d[j+g]==-1)
                        d[j+g]=d[j]+p;
                    else
                        if(d[j]+p<d[j+g])
                            d[j+g]=d[j]+p;
                }
            }
        }
        if(dr<gmax)
            dr=dr+g;
    }
    if(min!=2000000000)
        printf("%d\n",min);
    else
        printf("-1\n");
    return 0;
}