#include <bits/stdc++.h>

using namespace std;

int g;
int w,sum=0;
int mn[10001];
int nou[10001];

int main() {
  freopen ("energii.in", "r", stdin);
  freopen ("energii.out", "w", stdout);

  cin >> g;
  mn[0] = 0;
  for (int i = 1; i < 10001; i++) {
    mn[i] = 1e9;
  }

  cin >> w;
  for (int i = 1; i <= g; i++) {
    int e, p;
    cin >> e >> p;
    sum = sum+e;
    for (int j = 0; j < 10001; j++) {
      nou[j] = mn[j];
      if (j >= e) {
        int potential = mn[j - e] + p;
        if (potential < nou[j]) {
          nou[j] = potential;
        }
      }
    }

    for (int j = 0; j < 10001; j++) {
      mn[j] = nou[j];
    }

  }

  /// mn[consum total] = cat mai mic posibil
  /// conum total >= w

  int solutie = 1e9;
  for (int consumtotal = w; consumtotal < 10001; consumtotal++) {
    int pret = mn[consumtotal];
    if (pret < solutie) {
      solutie = pret;

    }
  }
  if (sum < w)
  {
      cout<<-1;
  }
  else
  {


  cout << solutie << "\n";
  }
}