#include <fstream>

using namespace std;

ifstream fin( "energii.in" );
ofstream fout( "energii.out" );

const int GMAX = 1000;
int v[GMAX + 1];

int main() {
  int n, i, j, p, c, g;
  fin >> n >> g;
  for( i = 1; i <= g; ++i )
    v[i] = (1 << 30);
  for( i = 0; i < n; ++i ){
    fin >> p >> c;
    for( j = g; j >= 0; --j ){
      if( j - p >= 0 )
        v[j] = min(v[j], c + v[j - p]);
      else
        v[j] = min(v[j], c);
    }
  }
  fout << (v[g] == (1 << 30) ? -1 : v[g]);
  return 0;
}