#include <iostream>
using namespace std;
typedef long long ll;
int main() {
	int N; cin >> N;
	ll res = 0;
	for (int i = 0; i < N; i++){
		ll b = 1;
		int c; cin >> c;
		for (int i = 0; i < c; i++){
			b *= 2;
		}
		res += b;
	}
	int ans = 0;
	while (res > 1){
		res /= 2LL;
		ans++;
	}
	cout << ans << endl;
	return 0;
}