#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (ll i = 0; i < (ll)(n); i++)
#define ll long long
const long long mod=998244353;
const long long hmod=46216567629137;
ll solve(ll a){
    ll res=0;
    while(a%2==0){
        res++;
        a/=2;
    }
    return res;
}
int main(){
    cin.tie(0)->sync_with_stdio(0);
    cout.tie(0);
    int N;
    cin>>N;
    ll A[N+1],B[N+1];
    ll ans=0;
    ll cnt[4];
    rep(i,4) cnt[i]=0;
    for(int i=1;i<=N;i++){
        cin>>A[i]>>B[i];
        ll c=solve(A[i]);
        if(c>=3){   
            cnt[3]+=B[i];
        }
        else if(c==2){
            cnt[2]+=B[i];
        }
        else if(c==1){
            cnt[1]+=B[i];
        }
    }
    ans+=cnt[3];
    if(cnt[2]>=cnt[1]){
        ans+=cnt[1];
        cnt[2]-=cnt[1];
        ans+=cnt[2]/2;
    }
    else{
        ans+=cnt[2];
        cnt[1]-=cnt[2];
        ans+=cnt[1]/3;
    }
    cout<<ans<<endl;
}