#include #include #include #include using namespace std; #define RREP(i,s,e) for (i = s; i >= e; i--) #define rrep(i,n) RREP(i,n,0) #define REP(i,s,e) for (i = s; i < e; i++) #define rep(i,n) REP(i,0,n) #define INF 100000000 typedef long long ll; int main() { int i, n; double l, r; ll k; int L[200000]; cin >> n; rep (i,n) cin >> L[i]; cin >> k; l = 0; r = 1000000000; while (l+1e-9 < r && l*(1+1e-9) < r) { double m = (l+r) / 2; ll sum = 0; rep (i,n) sum += L[i]/m; if (sum < k) r = m; else l = m; } cout << fixed << setprecision(10) << r << endl; return 0; }