#include<iostream>
#include<algorithm>
#define endl '\n'
using namespace std;

const int maxnn=100001;
int n;
long long a[maxnn];

void read()
{

    cin>>n;

    for(int i=0; i<n; ++i)
    {
        cin>>a[i];
    }

    sort(a, a+n);

    int maxn=0;
    int maxx=a[n-1];
    int maxxx=maxx;

    for(int i=n-1; i>=0; --i)
    {
        a[i]-=maxx;
        maxx--;
        if(a[i]>0)
        {
            if(a[i]>maxn)
            {
                maxn=a[i];
            }
        }
    }
    int ans=maxxx+maxn;
    cout<<ans<<endl;
}

int main()
{

    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);

    freopen("destruction", "r", stdin);
    freopen("destruction", "w", stdout);

	read();
    return 0;
}