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#include <bits/stdc++.h>

using namespace std;

#define PB push_back
#define FORE(i, t) for(__typeof(t.begin())i=t.begin();i!=t.end();++i)
#define SZ(x) int((x).size())
#define REP(i, n) for(int i=0,_=(n);i<_;++i)
#define FOR(i, a, b) for(int i=(a),_=(b);i<=_;++i)
#define FORD(i, a, b) for(int i=(a),_=(b);i>=_;--i)

#ifdef DEBUG
#define DEB(x) (cerr << x)
#else
#define DEB(x)
#endif

typedef long long ll;
typedef vector<int> vi;
typedef pair<int, int> pii;

const int MAX_A = 201800;

int counter[MAX_A];

void inline one() {
    int n;
    cin >> n;
    REP (i, n) {
        int x;
        cin >> x;
        ++counter[x];
    }
    int result = 0;
    REP (i, MAX_A) {
        if (counter[i] > 0) {
            result = i;
            counter[i + 1] += counter[i] / 2;
            counter[i] %= 2;
        }
    }
    cout << result << "\n";
}

int main() {
    ios::sync_with_stdio(false);
    //int z; cin >> z; while(z--)
    one();
}