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// Lupus Nocawy 21 XI 2017, PA2017
// http://potyczki.mimuw.edu.pl/
// Runda 1
// Zadanie: SKA
// Skarbonka [B]

#include <cstdio>
#include <iostream>
using namespace std;
#define REP(i,n) for(int i=0, _n=n; i<_n; ++i)
#define FOR(i,a,b) for(int i=(a), _b=(b); i<=_b; ++i)

const int max_n = 1000000;
const int max_a = 201718;

int C[max_a+1];

int main(void){
	int n;
	scanf("%d ", &n);
	REP(i,n){
		int c;
		scanf("%d ", &c);
		C[c]++;
	}
	FOR(i,0,max_a-1){
		C[i+1] += C[i]/2;
	}
	int max_i = max_a;
	while(C[max_i]==0)
		max_i--;
	int b = max_i;
	while(C[max_i]>1){
		b++;
		C[max_i]/=2;
	}
	printf("%d\n", b);
	return 0;
}