#include <bits/stdc++.h>
using namespace std;
using ll = int64_t;
#define rep(i, s, e) for (int i = s; i < e; ++i)
#define sort_(a) stable_sort(a.begin(), a.end())
#define rsort(a) stable_sort(a.rbegin(), a.rend())
#define join(a, d) accumulate(a.begin() + 1, a.end(), a[0], [](string s, string t) { return s + d + t; })
constexpr ll sum(auto a) { return accumulate(a.begin(), a.end(), 0LL); }
constexpr double degrees(double a) { return a * 180.0 / M_PI; }
constexpr double radians(double a) { return (a * M_PI) / 180.0; }
constexpr long mod = 1e9 + 7;

int main(int, [[maybe_unused]] char *argv[]) {
#ifdef DEBUG
  freopen(argv[1], "r", stdin);
#endif

  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout << fixed << setprecision(15);

  int N;
  cin >> N;
  vector<vector<int>> AB(N, vector<int>(2));
  rep(i, 0, N) cin >> AB[i][0] >> AB[i][1];

  ll ans = 0;
  ll n4 = 0;
  ll even = 0;
  rep(i, 0, N) {
    if (AB[i][0] % 8 == 0)
      ans += AB[i][1];
    else if (AB[i][0] % 4 == 0)
      n4 += AB[i][1];
    else if (AB[i][0] % 2 == 0)
      even += AB[i][1];
  }

  if (n4 < even) {
    ans += n4;
    ans += (even - n4) / 3;
  } else {
    ans += even;
  }

  cout << ans << endl;
  return 0;
}