#include<bits/stdc++.h>

using namespace std;

typedef long long int64;

int N, RPerf[100];

double F(int n)
{
  double latte = 0.0, malta = 0.0;
  for(int i = 1; i <= n; i++) latte += pow(0.81, i);
  for(int i = 1; i <= n; i++) malta += pow(0.9, i);
  return (sqrt(latte) / malta);
}

double f(int n)
{
  return ((F(n) - 0.229416) / (F(1) - 0.229416) * 1200.0);
}

double g(double x)
{
  return (pow(2.0, x / 800.0));
}

double g_inv(double x)
{
  return (800.0 * log(x) / log(2));
}

double rating(int n)
{
  double latte = 0.0, malta = 0.0;
  for(int i = 1; i <= N; i++) latte += g(RPerf[i - 1]) * pow(0.9, i);
  for(int i = 1; i <= N; i++) malta += pow(0.9, i);
  return (g_inv(latte / malta) - f(n));
}

int main()
{
  cin >> N;
  for(int i = 0; i < N; i++) cin >> RPerf[i];
  cout << (int)rating(N) << endl;
}