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#include <stdio.h>

using namespace std;
typedef long long LL;
typedef unsigned long long ULL;

#define IOSWORK ios::sync_with_stdio(0); cin.tie(0)
#define FOR(x, b, e) for(int x = b; x<= (e); x++)
#define FORD(x, b, e) for(int x = b; x>= (e); x--)
#define REP(x, n) for(int x = 0; x<(n); ++x)
#define ALL(c) (c).begin(), (c).end()
#define SIZE(x) ((int)(x).size())
#define VAR(v, n) typeof(n) v = (n)
#define FOREACH(i, c) for(VAR(i, (c).begin()); i != (c).end(); ++i)

#define SCAN_INT(n) scanf("%i",&n)
#define SCAN_P_INT(n,m) scanf("%i %i",&n,&m)
#define PRINT_P_INT(n,m) printf("%i %i\n",n,m);
#define PRINT_INT(n) printf("%i\n",n)


#define PB push_back
#define IN insert
#define ST first
#define ND second
#define INF 1000000007


#define MAXSIZE 250000

int a[MAXSIZE]={0};
int n;
int wynik = 0;

int main(){
	
	SCAN_INT(n);
	REP(i,n){
		int temp;
		SCAN_INT(temp);
		a[temp]++;
	}


	REP(i,MAXSIZE){
		if(a[i]!=0){
			wynik=i;
			a[i+1]+=a[i]/2;
		}
	}
	PRINT_INT(wynik);
   return 0;
}