#include <bits/stdc++.h>
using namespace std;
#define REP(i,a,n) for(int i=(a); i<(int)(n); i++)
#define rep(i,n) REP(i,0,n)
#define FOR(it,c) for(__typeof((c).begin()) it=(c).begin(); it!=(c).end(); ++it)
#define ALLOF(c) (c).begin(), (c).end()
typedef long long ll;
typedef unsigned long long ull;

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

double invg(double g){
  return 800.0 * (log(g)/log(2.0));
}

int main(){
  int N;
  cin >> N;
  vector<double> v;
  rep(i,N){
    double a;
    cin >> a;
    v.push_back(a);
  }

  double finf = 0.229415733870562;
  double f1 = 1.0;
  
  double a = 0;
  double b = 0;
  double c = 0;
  REP(i,1,N+1){
    double tmp = pow(0.9, i);
    a += g(v[i-1]) * tmp;
    b += tmp;
    c += pow(0.81, i);
  }

  double fn = (sqrt(c) / b) - finf;
  fn /= (f1 - finf);
  fn *= 1200.0;
  
  double rating = invg(a/b);
  rating -= fn;

  cout << (int)rating << endl;
  
  return 0;
}