#include <bits/stdc++.h>
using namespace std;

using int64 = long long;
using uint64 = unsigned long long;

constexpr long double Finf = sqrtl(0.81 / (1 - 0.81)) / (0.9 / (1 - 0.9));

long double F(int n)
{
    long double a = 0, b = 0;
    for (int i = 0; i < n; i++)
    {
        a += powl(0.81, i + 1);
        b += powl(0.9, i + 1);
    }
    return sqrtl(a) / b;
}

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

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

// log_a bを計算
long double log(long double a, long double b)
{
    return logl(b) / logl(a);
}

long double ginv(long double x)
{
    return 800 * log(2.0, x);
}

int rating(vector<int> perf)
{
    long double a = 0, b = 0;
    int n = perf.size();

    for (int i = 0; i < n; i++)
    {
        a += g(perf[i]) * powl(0.9, i + 1);
        b += powl(0.9, i + 1);
    }
    return (int)(ginv(a) - ginv(b) - f(n) + 0.000005);
}

int main()
{
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    int N;
    cin >> N;

    vector<int> perf(N);
    for (int i = 0; i < N; i++)
    {
        cin >> perf[i];
    }

    cout << rating(perf) << endl;

    return 0;
}