#include<cstdio>
using namespace std;
int G,W,v[10005],maxim,c,p;
int main()
{
    freopen("energii.in","r",stdin);
    freopen("energii.out","w",stdout);
    scanf("%d",&G);
    scanf("%d",&W);
    for(int i=1;i<=10005;i++) v[i]=999999;
    v[0]=0;
    maxim=0;
    for (int i=1;i<=G;i++)
    {
        scanf("%d%d",&p,&c);
        for(int j=0;j<=W;j++)
        {
            if (v[j+p]==999999 || v[j+p]>(v[j]+c))
            {
                v[j+p]=v[j]+c;
                if ((j+p)>maxim) maxim=j+p;
            }
        }
    }
    int i=W;
    bool ok=0;
    while (!ok && i<10005)
    {
        if (v[i]!=999999)
        {
            ok=1;
            printf("%d\n",v[i]);
        }
    }
    if (!ok) printf("-1\n");
    return 0;
}