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#include <algorithm>
#include <iostream>
#include <cassert>
#include <vector>
#include <cstdio>
#include <array>
#include <deque>
#include <cmath>
#include <stack>
#include <queue>
#include <set>
#include <map>
namespace {
	using namespace std;

	typedef vector<int> vint;
	typedef long long unsigned ulo;
	typedef long long lint;
	
	void __attribute__((unused)) spacje(int k) {
		int magic;
		static stack<int*> stos;
		while (!stos.empty() && stos.top() <= &magic) stos.pop();
		stos.push(&magic);
		for (int n = k * stos.size(); n--;) fprintf(stderr, " ");
	}

    #define BEND(x) begin(x), end(x)
	
	#define BOTH(x) for (int x = 0; x < 2; ++x)
	
	#define UPlt(xx, yy) (xx) = min(xx, yy)
	#define UPgt(xx, yy) (xx) = max(xx, yy)
	
	struct in_t {
		template<class T>
		operator T () {
			static bool __attribute__((unused)) dummy = ios_base::sync_with_stdio(false);
			T x;
			cin >> x;
			return x;
		}
	};
	in_t __attribute__((unused)) in;
	
	class Print {
		ostream & os;
		bool nfirst;
	 public:
		Print(ostream & os = cout) : os(os), nfirst(false) {}
		~Print() { os << endl; }
		template<class T> Print & operator , (T const& e) {
			if (nfirst) os << " ";
            os << e; nfirst = true; return *this;
        }
	};
	
	#define print Print{cout},
	#define prerr Print{cerr},
	
	template <class T>
	struct Range {
		struct Intit {
			T x; Intit(T x) : x(x) {}
			T & operator * () { return x; };
			bool operator != (Intit other) { return x < other.x; }
			void operator ++ () { ++x; }
		};
		
		T b, e;
		explicit Range(T n) : b(0), e(n) {}
		Range(T b, T e) : b(b), e(e) {}
		Intit begin() { return b; }
		Intit end() { return e; }
	};
	
	template <class T>
	Range<T> range(T n) { return Range<T>(n); }
	
	template <class T>
	Range<T> range(T b, T e) { return Range<T>(b, e); }

	template <class T>
	Range<T> inclusive(T b, T e) { return Range<T>(b, e + 1); }
	
	#define _ __attribute__((unused)) _
};

#define dprintf(...) if (1) spacje(2), fprintf(stderr, __VA_ARGS__)

struct Vec {
    vector<int> v;

    int size() const { return v.size(); }

    int & operator [] (int i) {
        if (i >= size()) {
            v.resize(i + 1, 0);
        }
        return v.at(i);
    }
};

int main() {
    int n = in;

    Vec v;

    for (int _ : range(n)) {
        v[in] += 1;
    }

    for (int i = 0; i < v.size(); ++i) {
        int x = v[i];
        int next = x / 2;
        if (next != 0) {
            v[i + 1] += next;
        }
    }

    print v.size() - 1;

	return 0;
}