ABC138B - Resistors in Parallel

問題：B - Resistors in Parallel

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

#define REP(i, n) for (int i = 0; i < (n); ++i)

int main(void) {
    int n, a;
    double ans = 0.0;

    cin.tie(0);
    ios::sync_with_stdio(false);
    cin >> n;
    REP(i, n) {
        cin >> a;
        ans += 1.0 / (double) a;
    }

    cout << fixed << setprecision(10) << 1.0 / ans << "\n";
    return 0;
}