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#include<stdio.h>
#include<iostream>
#include<math.h>


using namespace std;

int main()

{
	

unsigned long int n=0;
unsigned long int in=0;
unsigned long int w=0;
unsigned long int i=0;
cin>>n;

for(i=0;i<n;i++)
{
cin>>in;
w=w+pow(2,in);	
	
	
	
}


	
	cout<<trunc(log2(w));
	
	
	
	
	
	
	
}