#include <stdio.h>
#include <atcoder/all>
#include <bits/stdc++.h>
using namespace std;
using namespace atcoder;
using mint = modint998244353;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf32 1000000005
#define Inf64 1000000000000000001LL

int main(){
	
	int n;
	cin>>n;
	
	long long c1 = 0,c2 = 0;
	long long ans = 0;
	rep(i,n){
		long long a,b;
		cin>>a>>b;
		swap(a,b);
		int c = 0;
		while(b%2==0){
			c++;
			b /= 2;
		}
		if(c>=3)ans += a;
		else{
			if(c==1)c1 += a;
			if(c==2)c2 += a;
		}
	}
	if(c2 <= c1){
		ans += c2;
		ans += (c1-c2)/3;
	}
	else{
		ans += c1;
		ans += (c2-c1)/2;
	}
	cout<<ans<<endl;
	
}