1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
#include<bits/stdc++.h>
using namespace std;

#define REP(i, M) for(int i = 0; i < M; i++)
#define R(p, k) for(int i = p; i <= k; i++)
#define RI(j, p, k) for(int j = p; j <= k; j++)
#define PB push_back
#define FI first
#define SE second
#define LL long long 


#define DEB 1

#if DEB
	#define CEN cerr << endl;
	#define CEL(a) cerr << #a << ": " << a << " "; 
	#define CES(s) cerr << s << endl;
#else
	#define CEN 
	#define CEL(a) 
	#define CES(s) 
#endif

//const int MN = 10;
const int MN = 1000 * 1000;
int kub[MN];
int n, a, res;

int main(){
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
        cin >> n;
        for(int i = 0; i<n; i++){
            cin >> a;
            kub[a]++;
        }
        
        for(int i = 0; i + 1 < MN; i++){
            //cerr << i << " " << kub[i] << endl;
            if(kub[i] > 0)
                res = i;
            kub[i + 1] += kub[i]/2;
        }
        cout << res << endl;
	return 0;
}