#include <cstdio>
#include <cstring>
#include <iostream>
#include <vector>
#include <algorithm>
#include <set>
#include <stack>
#include <queue>
#include <list>
#include <map>
#include <bitset>
//#include <windows.h>
//#include <conio.h>
#include <cstdlib>
#include <time.h>
#include <limits.h>
#include <string>
#include <cmath>
#include <iomanip>
using namespace std;
#define forA(V,it) for (typeof(V.begin()) it=V.begin();it!=V.end();it++)
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define ll long long
#define ull unsigned ll
#define MOD 666013
#define INF (1<<31)-1
#define MINF -(1<<31)
#define vi vector <int>
#define vll vector <ll>
#define pii pair <int,int>
#define pll pair <ll,ll>
#define newl printf("\n")
#define DIM 1005
int N,i,v[100005],st[100005],ap[100005],lvl;
int main()
{
    //freopen("patrate6.in","r",stdin);
    //freopen("patrate6.out","w",stdout);
    scanf("%d",&N);
    for (i=1;i<=N;i++) scanf("%d",&v[i]);
    sort(v+1,v+N+1);
    st[++lvl]=v[N]; ap[lvl]=1;
    for (i=N-1;i>0;i--)
    {
        if (v[i]==st[lvl])
        {
            ap[lvl]++;
            if (ap[lvl]==4)
            {
                if (lvl==1 || st[lvl-1]!=st[lvl]+1) st[lvl]++,ap[lvl]=1;
                else
                {
                    while (st[lvl-1]==st[lvl]+1 && ap[lvl]==4 && lvl>1)
                    {
                        ap[lvl-1]++;
                        lvl--;
                    }
                    if (ap[lvl]==4) st[lvl]++,ap[lvl]=1;
                }
            }
        }
        else st[++lvl]=v[i],ap[lvl]=1;
    }
    if (lvl==1 && ap[1]==1) printf("%d",st[1]);
    else printf("%d",st[1]+1);
    return 0;
}