#include <fstream>

#define Nmax 5005
#define MAX 999999999

using namespace std;

ofstream fout("energii.out");
/*

void show(int V[], int W, int min, int max)
      {int i;
       for(i=0; i<=W+10; i++)
           fout<<V[i]<<" ";
       fout<<" *** "<<min<<" *** "<<max<<'\n';
       }     
          
*/      
      

int main(void)
    {int V[Nmax]={0}, n, C[Nmax], W, E[Nmax];
     ifstream fin("energii.in");
     fin>>n>>W;
     int i;
     for(i=1;i<=n; i++)
        fin>>E[i]>>C[i];
     fin.close();
     V[0]=1;
     int min=MAX, max=0, k, m;
     int j;
     for(i = 1; i <= n; ++i) 
     {
         for(j = max; j >= 0; --j)
              if(V[j]) {
                  k = E[i] + j;
                  if(!j) 
                     m = 0;
                  else 
                     m = V[j];
                  if(k > W) { 
                      if(m + C[i] < min) 
                          min = m + C[i]; 
                  }
                  else if (!V[k]) 
                       V[k] = m + C[i];
                  else if (m + C[i] < V[k]) 
                       V[k] = m + C[i];
               }
         max += E[i];
         if (max > W)
            max = W;
     }
     if(min == MAX && V[W] == 0) { 
         fout<<"-1\n"; 
         fout.close(); 
         return 0;
     }
     
     fout<<min<<'\n';
     
     fout.close();
     
     return 0;
}