#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define all(x) (x).begin(), (x).end()
using ll = long long;
const ll MOD = 998244353;
#include<atcoder/all>
using namespace atcoder;
using mint = modint998244353;

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  ll n;cin>>n;
  ll ans=0;
  rep(i,n){
    ll a,b;cin>>a>>b;
    ll cnt=0;
    while(a%2==0){
        a/=2;
        cnt++;
    }
    ans+=min(ll(3),cnt)*b;
  }
  cout<<ans/3<<endl;
}