#include <bits/stdc++.h>

using namespace std;

const int INF = 1<<30;

double gsum(double a, int n) {
  return n == INF ? a / (1-a) : (a - pow(a, n+1)) / (1 - a);
}

double F(int n) {
  double num = sqrt(gsum(0.81, n));
  double den = gsum(0.9, n);
  return num / den;
}

double f(int n) {
  return (F(n) - F(INF)) / (F(1) - F(INF)) * 1200;
}

double g(double x) {
  return pow(2.0, x/800);
}

double invg(double x) {
  return 800 * log(x) / log(2.0);
}

double rating(const vector<double> perf) {
  int n = perf.size();
  double sum = 0;
  for (int i = 0; i < n; i++)
    sum += g(perf[i]) * pow(0.9, i + 1);
  sum /= gsum(0.9, n);
  return invg(sum) - f(n);
}

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

  int n;
  cin >> n;
  vector<double> perf(n);
  for (int i = 0; i < n; i++)
    cin >> perf[i];

  int ret = rating(perf) + 0.5;
  cout << ret << endl;
  
  return 0;
}