#include <iostream>
#include <iomanip>
using namespace std;

int main()
{
    int n;
    cin >> n;
    double a[105];
    for(int i = 0; i < n - 1; i++)
    {
        cin >> a[i];
    }
    double s = 1000;
    for(int i = 0; i < n - 1; i++)
    {
        s -= a[i] * s / 1000;
    }
    cout << fixed << setprecision(15) << 1000 - s << endl;
}