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#include <bits/stdc++.h>
using namespace std;
int main ()
{
	int n;
	unsigned long long x=1;
	int y=0;
	unsigned long long d;
	unsigned long long suma=0;
	cin>>n;
	int a;
	for(int i=0; i<n; ++i)
	{	d=1;
		cin>>a; 
		for(int j=0; j<a; ++j)
			d=d*2; 
		suma+=d;
	}
	while(x<=suma) 
	{
		y++;
		x=x*2;
	}
	y--;
	cout<<y<<endl;
}