#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main()
{
  int n;
  cin >> n;
  vector<long long> cnt(3);
  long long ans = 0;
  for (int i = 0; i < n; ++i)
  {
    int a, b;
    cin >> a >> b;
    int c = 0;
    while (a % 2 == 0)
    {
      ++c;
      a /= 2;
    }
    if (c >= 3)
    {
      ans += b;
      continue;
    }
    cnt[c] += b;
  }
  long long tmp = min(cnt[1], cnt[2]);
  ans += tmp;
  cnt[1] -= tmp;
  cnt[2] -= tmp;
  ans += cnt[1] / 3 + cnt[2] / 2;
  cout << ans << endl;
}