#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
#define ll long long
#define rep(i,a,b) for(int i=(a);i<(b);i++)
#define repl(i,a,b) for(ll i=(a);i<(b);i++)
#define all(a) (a).begin(),(a).end()

template <typename T> bool chmin(T &a,T b){if(a>b){a=b;return true;} return false;}
template <typename T> bool chmax(T &a,T b){if(a<b){a=b;return true;} return false;}

int main(){
  ll n; cin >> n;
  ll x=0,y=0,z=0;
  rep(i,0,n){
    ll a,b; cin >> a >> b;
    if(a%8 == 0){
      x+=b;
    }
    else if(a%4 == 0){
      y+=b;
    }
    else if(a%2 == 0){
      z+=b;
    }
  }
  ll ans=x;
  if(y>=z){
    ans+=z;
    y-=z;
    z=0;
    ans+=y/2;
  }
  else{
    ans+=y;
    z-=y;
    y=0;
    ans+=z/3;
  }
  cout << ans << endl;
}