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
48
49
#include <bits/stdc++.h>

#define FOR(i,b,e) for(int i=(b); i <= (e); ++i)
#define FORD(i,b,e) for(int i=(b); i >= (e); --i)
#define SIZE(c) (int) (c).size()
#define FORE(i,c) FOR(i,0,SIZE(c)-1)
#define FORDE(i,c) FORD(i,SIZE(c)-1,0)

#define pb push_back
#define mp make_pair
#define st first
#define nd second


using namespace std;


const int N = 300000;
int cnt[N];

/*************************************************************************/

int main() {
    ios_base::sync_with_stdio(0);
    
    int n;
    cin >> n;

    while (n--) {
        int x;
        cin >> x;
        
        cnt[x]++;
    }
    
    FOR(i,0,N-2) {
        cnt[i+1] += cnt[i] / 2;
        cnt[i] %= 2;
    }
    
    int ans = N-1;
    while (cnt[ans] == 0) ans--;
    
    cout << ans;

    return 0;
}

/*************************************************************************/