#include <bits/stdc++.h>
#define FOR(i,bg,ed) for(ll i=(bg);i<(ed);i++)
#define REP(i,n) FOR(i,0,n)
#define MOD 1000000007
#define int long long
using namespace std;
typedef long long ll;
typedef vector<vector<ll>> mat;
const int INF = 1e9;

double F(int n)
{
    double bunsi = 0.0;
    for (int i=1; i<=n; i++) {
        bunsi += pow(0.81, i);
    }
    bunsi = sqrt(bunsi);

    double bunbo = 0.0;
    for (int i=1; i<=n; i++) {
        bunbo += pow(0.9, i);
    }

    return bunsi / bunbo;
}

double f(int n)
{
    return 1200.0 * (F(n) - F(10000)) / (F(1) - F(10000));
}

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

double gInv(double y)
{
    return 800.0 * log(y) / log(2);
}

signed main()
{
    int N;
    int RPerf[110];

    cin >> N;
    REP(i,N) cin >> RPerf[i+1];

    double bunsi = 0.0;
    for (int i=1; i<=N; i++) {
        bunsi += g(RPerf[i]) * pow(0.9, i);
    }

    double bunbo = 0.0;
    for (int i=1; i<=N; i++) {
        bunbo += pow(0.9, i);
    }

    double ans = gInv(bunsi / bunbo) - f(N);

    cout << (int)(ans + 0.5) << endl;
}