#include <stdio.h>
int g,w,eg[1001],cg[1001],a[20000],min;
int main()
{
    freopen("energii.in","r",stdin);
    freopen("energii.out","w",stdout);
    scanf("%d\n%d\n",&g,&w);
    int i,j;
    for (i=1;i<=12000;i++)
        a[i]=-1;
    for (i=0;i<g;i++)
    {
        scanf("%d %d\n",&eg[i],&cg[i]);
        for (j=w;j>0;j--)
            if (a[j]>=0&&(a[j+eg[i]]>a[j]+cg[i]||a[j+eg[i]]==-1))
                a[j+eg[i]]=a[j]+cg[i];
        if (a[eg[i]]>cg[i]||a[eg[i]]==-1)
            a[eg[i]]=cg[i];
    }
    for (i=w;!a[i];i++);
    min=a[i];
    for (;i<=12000;i++)
        if (a[i]>=0&&a[i]<min)
            min=a[i];
    printf("%d\n",min);
    return 0;
}