#include <fstream>
#include<algorithm>
using namespace std;
ifstream fin("energii.in");
ofstream fout("energii.out");
pair<int,int>v[10005];
int n,i,g,e,j;
long long st[10005],dr[10005],cost1,cost2,s;
int main()
{
    fin>>g>>e;
    for(i=1;i<=g;i++)
        {fin>>v[i].first>>v[i].second;
        s+=v[i].first;}
    if(s<e)
    {
        fout<<-1;
        return 0;
    }
    sort(v+1,v+g+1);
   st[1]=v[1].first;
   i=1;
   while(st[i]<e&&i+1<=g)
   {
       st[++i]=st[i-1]+v[i].first;
   }
   for(j=1;j<=i;j++)
      cost1+=v[j].second;
   dr[g]=v[g].first;
   i=g;
   while(dr[i]<e&&i-1>=1)
   {
       dr[--i]=dr[i+1]+v[i].first;
   }
   for(j=g;j>=i;j--)
    cost2+=v[j].second;
   fout<<min(cost1,cost2);
    return 0;
}