#include <bits/stdc++.h>
using namespace std;
ifstream in("energii.in");
ofstream out("energii.out");
const int GMAX = 5000;
int v[1005], w[1005], dp[1005][10005];
int main() {
  int n, g;
  in >> n >> g;
  for (int i = 1; i <= n; i++) {
  in >> v[i] >> w[i];
  }
  for (int i = 1; i <= n; i++)
  for (int j = 1; j <= g; j++) dp[i][j] = 2e9;
  dp[1][v[1]] = w[1];
  for (int i = 2; i <= n; i++) {
    for (int j = 1; j <= g; j++) {
      if (j >= v[i]) {
        dp[i][j] = min(dp[i - 1][j], dp[i - 1][j - v[i]] + w[i]);
      }
      else {
        dp[i][j] = min(dp[i - 1][j] , w[i]);
      }
    }
  }
  if (dp[n][g] == 2e9) return out << -1, 0;
  return out << dp[n][g] << "\n", 0;
}