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

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int N; cin >> N;
    long long one = 0,two = 0,three = 0;
    while(N--){
        int a,b; cin >> a >> b;
        int c = 0;
        while(a%2 == 0) a /= 2,c++;
        c = min(c,3);
        if(c == 1) one += b;
        if(c == 2) two += b;
        if(c == 3) three += b; 
    }
    long long answer = three;
    long long v = min(one,two);
    answer += v;
    one -= v,two -= v;
    answer += one/3;
    answer += two/2;
    cout << answer << endl;
}