#include <bits/stdc++.h>

using namespace std;
using ll = long long;
using ull = unsigned long long;
template <class T>
using max_heap = priority_queue<T>;
template <class T>
using min_heap = priority_queue<T, vector<T>, greater<>>;
ll ll_min = numeric_limits<ll>::min();
ll ll_max = numeric_limits<ll>::max();
ll ALPHABET_N = 26;
static const ll INF = ll_max / 10;
#define rep(i, n) for (ll i = (ll)0; i < (ll)n; i++)
#define rep_(i, k, n) for (ll i = (ll)k; i < (ll)n; i++)
#define all(a) a.begin(), a.end()

int main()
{
	ios::sync_with_stdio(false);
	cin.tie(0);
	ll n;
	cin >> n;
	ll cnt1 = 0, cnt2 = 0, over3 = 0;
	rep(i, n)
	{
		ll a, b;
		cin >> a >> b;
		ll cnt = 0;
		while (a % 2 == 0 && cnt < 3)
		{
			a /= 2;
			cnt++;
		}
		if (cnt == 1)
			cnt1 += b;
		else if (cnt == 2)
			cnt2 += b;
		else if (cnt >= 3)
			over3 += b;
	}
	ll ans = over3;
	ll pair1_2 = min(cnt1, cnt2);
	ans += pair1_2;
	cnt1 -= pair1_2;
	cnt2 -= pair1_2;
	ans += cnt1 / 3;
	ans += cnt2 / 2;
	cout << ans << endl;
	return 0;
}