#include <iostream>
#include <fstream>
#include <cstdio>
#include <cmath>
#include <vector>
#include <cstring>
#include <string>
#include <set>
#include <map>
#include <stack>
#include <queue>
#include <algorithm>
using namespace std;

#define REP(i,n) for(int i=0; i<n; ++i)
#define FOR(i,a,b) for(int i=a; i<=b; ++i)
#define FORR(i,a,b) for (int i=a; i>=b; --i)
#define ALL(c) (c).begin(), (c).end()

typedef long long ll;
typedef vector<int> VI;
typedef vector<ll> VL;
typedef vector<VI> VVI;
typedef vector<VL> VVL;
typedef pair<int,int> P;
typedef pair<ll,ll> PL;

double F(int n){
    double a = 0, b = 0;
    FOR(i,1,n){
        a += pow(0.81, i);
        b += pow(0.9, i);
    }
    return sqrt(a) / b;
}

double f(int n){
    return 1200.0 * (F(n) - F(1e5)) / (F(1) - F(1e5));
}

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

double ginv(double x){
    double l = -100, r = 1e9;
    REP(i,100){
        double mi = (l + r) / 2;
        if (g(mi) > x) r = mi;
        else l = mi;
    }
    return l;
}

int main(){
    int n;
    cin >> n;
    double a = 0, b = 0;
    REP(i,n){
        double p;
        cin >> p;
        a += g(p) * pow(0.9, (i+1));
        b += pow(0.9, (i+1));
    }
    // cout << ginv(a/b) << " " << f(n) << endl;
    printf("%d\n", (int)(ginv(a/b) - f(n)));
    return 0;
}