#include<stdio.h>
int n,w,wmax,e,i,j,g;
long a[10000],s;
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",&e,&g);
  for(j=wmax;j>=0;j--)
   if(a[j+e]==0||a[j+e]>a[j]+g) {a[j+e]=a[j]+g;
                      if(j+e>wmax) wmax=j+e;}}
 if(a[w]) s=a[w];
 else s=-1;
 printf("%ld",s);
 fclose(stdout);
 return 0;}