#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <climits>
#include <vector>
#include <string>
#include <queue>
#include <deque>
#include <list>
#include <stack>
#include <set>
#include <map>
#include <unordered_set>
#include <unordered_map>
#include <algorithm>

#define int long long
#define MOD7 1000000007
#define MOD9 1000000009

#define rep(i, n) for (int i = 0; i < (n); i++)
#define itrep(i, a) for (auto i = (a).begin(); i != (a).end(); i++)
#define REP(i, a, n) for (int i = (a); i <= (n); i++)
#define all(a) (a).begin(), (a).end()

using namespace std;

int dx[4] = { 1, 0, -1, 0 };
int dy[4] = { 0, -1, 0, 1 };

template<class T> void inputVector(vector<T>& v, int n) {
    v.resize(n);
    for (int i = 0; i < v.size(); i++) cin >> v[i];
}

double F(int n) {
    double ret = 0;

    rep(i, n) ret += pow(0.81, i + 1);
    ret = sqrt(ret);

    double tmp = 0;
    rep(i, n) tmp += pow(0.9, i + 1);
    ret /= tmp;

    return ret;
}

double F_INF = F(1000000);

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

double g(int X) {
    return pow(2,  (double) X / 800);
}

double invg(double X) {
    double low = 0;
    double high = 100000;
    double mid = (high + low) / 2;

    int cnt = 100;
    while (cnt--) {
        if (g(mid) > X) {
            high = mid;
        } else {
            low = mid;
        }
        mid = (high + low) / 2;
    }

	cerr << "invg(" << X << ") = " << mid << endl;

    return mid;
}

signed main() {
    int N;
    cin >> N;

    vector<int> perf;
    inputVector(perf, N);

    double rating = -f(N);

    double tmp = 0;
    rep(i, N) tmp += g(perf[i]) * pow(0.9, i + 1);
    double tmp2 = 0;
    rep(i, N) tmp2 += pow(0.9, i + 1);
    tmp /= tmp2;

    rating += invg(tmp);

    cout << (int) rating << endl;

    return 0;
}