#include<stdio.h>

struct nod{ int e, c; } v[1024];
int n, w, cost[5020];

void solve()
{
  for(int i=1; i<=n; ++i) {
    for(int j=w-1; j>=0; --j) if( cost[j]!=-1)
      if( cost[j]+ v[i].c < cost[j+v[i].e] || cost[j+v[i].e]==-1) {
        if( j+v[i].e > w) cost[ w+1]= cost[j]+v[i].c;
        else cost[j + v[i].e]= cost[j]+ v[i].c;
      }
  }
}

int main()
{
  freopen("energii.in","r",stdin);
  scanf("%d\n%d",&n,&w);
  for(int i=1; i<=n; ++i) scanf("%d %d",&v[i].e, &v[i].c);

  for(int i=1; i<=5010; ++i) cost[i]=-1;

  solve();

  freopen("energii.out","w",stdout);

  if( cost[w]==-1) {
    if( cost[w+1]==-1) printf("-1\n");
    else printf("%d\n",cost[w+1]);
  }
  else {
    if( cost[w+1]==-1) printf("%d\n",cost[w]);
    else {
      if( cost[w+1] > cost[w]) printf("%d\n",cost[w]);
      else printf("%d\n",cost[w+1]);
    }
  }

  


  return 0;
}