#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define FAST1 ios_base::sync_with_stdio(false);
#define FAST2 cin.tie(NULL);
 
bool sort_on_second(pair<ll,ll> left, pair<ll,ll> right){
    return left.second<right.second;
}
void solve(){
    ll n;
    cin>>n;
    vector<pair<ll,ll>> arr(n);
    ll ans=0;
    for(ll i=0;i<n;i++)
    {
        cin>>arr[i].first>>arr[i].second;
        ans+=2*arr[i].first;
    }
    sort(arr.begin(),arr.end(),sort_on_second);
    reverse(arr.begin(),arr.end());
    ll i=0,j=n-1;
    ll cur =0;
    while(i<=j){
        ll tar=arr[j].second;
        if(i==j){
            ll can_take=arr[i].first;
            ll to_take=max(0ll,arr[i].second-cur);
            can_take=max(0ll,can_take-to_take);
            ans-=can_take;
            break;
        }
        else if(cur>=tar){
            cur+=arr[j].first;
            ans-=arr[j].first;
            j--;
        }
        else if(cur+arr[i].first<=arr[j].second){
            cur+=arr[i].first;
            arr[i].first=0;
            i++;
        }
        else{
            ll to_take=arr[j].second-cur;
            cur+=to_take;
            cur+=arr[j].first;
            arr[i].first-=to_take;;
            ans-=arr[j].first;
            j--;
        }
    }
    cout<<ans<<endl;
 
}
 
int main(){
    FAST1;
    FAST2;
    ll t=1;
    while(t--){
        solve();
    }
}
 

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