D

#include <bits/stdc++.h>

using namespace std;

#define ll     long long
#define ff     first
#define ss     second

int main()
{
    int n;
    cin>>n;

    vector<pair<int, ll int>> sc(n);
    for(auto &[s, c]: sc)   cin>>s>>c;

    set<ll int> sl;

    unordered_map<ll int, ll int> cnt;

    for(int i=0; i<n; i++)
    {
        sl.insert(sc[i].ff);
        cnt[sc[i].ff] = sc[i].ss;
    }

    while(sl.size())
    {
        auto s = *sl.begin();
        sl.erase(sl.begin());

        ll int x = (cnt[s]/2)*2;

        if(!x)      continue;

        cnt[s] -= x;
        cnt[2*s] += x/2;

        sl.insert(2*s);
    }

    ll int ans = 0;

    for(auto [s, c]: cnt)
        ans += c;

    cout<<ans<<"\n";
}