#include <stdio.h>
long power[22000],cost[22000],c[22000],pos[22000],i,n,w,sol,j,max;
int main()
{freopen("energii.in","r",stdin);
 freopen("energii.out","w",stdout);
 scanf("%ld%ld",&n,&w);pos[0]=1;
 for(i=1;i<=n;i++)
  {scanf("%ld%ld",&power[i],&c[i]);if(power[i]>max)max=power[i];
   for(j=w+power[i];j>=0;j--)
    if(pos[j])
     if(pos[j+power[i]]==0){pos[j+power[i]]=1;cost[j+power[i]]=cost[j]+c[i];}
      else
       if(cost[j]+c[i]<cost[j+power[i]])cost[j+power[i]]=cost[j]+c[i];
  }
 sol=1000000004;
 for(i=w+max;i>=w;i--)
  if(pos[i]&&cost[i]<sol)sol=cost[i];
 if(sol==1000000004)printf("-1");else printf("%ld",sol);
 fclose(stdin);fclose(stdout);
 return 0;
}