#include<cstdio>
#include<algorithm>
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]=1000000000;
for(i=1;i<=n;i++)
    {
    for(j=1;j<=w;j++)
        {
        if(j-v[i]<=0||(a[i-1][j-v[i]]<1000000000))
            {
            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]=1000000000;
        }
    }
if(a[n][w]!=1000000000)
    printf("%d",a[n][w]);
else
    printf("-1");
return 0;
}