#include<cstdio>
#include<algorithm>
#define INF 1000000000
using namespace std;
int a[1001][5001],v[1001],vc[1001],w,n,i,j;
int main ()
{
    freopen("energii.in","r",stdin);
    freopen("energii.out","w",stdout);

    scanf("%d%d",&n,&w);

    for(i=1; i<=n; i++)
        scanf("%d%d",&v[i],&vc[i]);

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

    for(i=1; i<=n; i++)
    {
        for(j=1; j<=w; j++)
        {
            if(j-v[i]<=0||(a[i-1][j-v[i]]<INF))
            {
                if(j-v[i]<=0)
                    a[i][j]=min(vc[i],a[i-1][j]);
                else
                    a[i][j]=min(vc[i]+a[i-1][j-v[i]],a[i-1][j]);
            }
            else
                a[i][j]=INF;
        }
    }

    if(a[n][w]!= INF)
        printf("%d",a[n][w]);
    else
        printf("-1");
    return 0;
}