#include <bits/stdc++.h>
using namespace std;
int main() {
  int TUX;
  cin >> TUX;
  int FOO = 0;
  int BAR = 0;
  int BAZ = 0;
  int QUZ = 1;
  while (TUX-- > 0) {
    int PUR;
    cin >> PUR;
    FOO = FOO + PUR;
    BAR = BAR + 1;
    if (max(FOO * QUZ, BAR * BAZ) == FOO * QUZ) {
      BAZ = FOO;
      QUZ = BAR;
    }
  }
  cout << fixed << setprecision(6) << (double)(BAZ) / QUZ;
}
