#include <bits/stdc++.h>
using namespace std;
using ll=long long;

int main(void) {
	int N;
	cin >> N;
	vector<int> A(N),B(N);
	for(int i = 0; i < N; ++i) cin >> A[i] >> B[i];
	
	vector<ll> cnt(4, 0);
	for(int i = 0; i < N; ++i) {
		int t = 0;
		while((A[i] & 1) == 0 and t < 3) {
			A[i] >>= 1;
			++ t;
		}
		cnt[t] += B[i];
	}
	
	ll ans = cnt[3];
	if(cnt[1] <= cnt[2]) ans += cnt[1] + (cnt[2] - cnt[1]) / 2;
	else ans += cnt[2] + (cnt[1] - cnt[2]) / 3;
	
	cout << ans << endl;
	return 0;
}