#include <cmath>
#include <iomanip>
#include <iostream>
using namespace std;
int n, p[109];
double f(int x) {
	double pa = 0.0, qa = 0.0;
	for (int i = 1; i <= x; i++) {
		pa += pow(0.81, i);
		qa += pow(0.9, i);
	}
	return sqrt(pa) / qa;
}
double g(int x) {
	return pow(2, x / 800.0);
}
int main() {
	cin >> n;
	for (int i = 0; i < n; i++) cin >> p[i];
	double F = (f(n) - f(10000)) / (f(1) - f(10000)) * 1200;
	double pa = 0.0, qa = 0.0;
	for (int i = 0; i < n; i++) {
		pa += g(p[i]) * pow(0.9, i + 1);
		qa += pow(0.9, i + 1);
	}
	cout << (int)(log2(pa / qa) * 800 - F + 0.5) << endl;
	return 0;
}