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#include<bits/stdc++.h>
#define ull unsigned long long
#define pb push_back
using namespace std;

bool t[ 213700 ];

int main()
{
	ios_base::sync_with_stdio(0);
	cin.tie(0);

    int n;
    cin >> n;
    for( int i = 0 ; i < n ; i++ )
    {
        int w;
        cin >> w;
        while( t[ w ] )
        {
            t[ w ] = false;
            w++;
        }
        t[ w ] = true;
    }
    for( int i = 213699 ; i >= 0 ; i-- )
    {
        if( t[ i ] )
        {
            cout << i << endl;
            return 0;
        }
    }
	return 0;
}