#include <bits/stdc++.h>
using namespace std;
int main() {
  int FOO = 0, BAR = 0, BAZ = 0, QUZ = 1, TUX, PUR;
  scanf("%d", &TUX);
  int i;
  for (i = 1; i <= TUX; i++) {
    scanf("%d", &PUR);
    FOO += PUR;
    BAR += 1;
    if (FOO * QUZ > BAZ * BAR) {
      BAZ = FOO;
      QUZ = BAR;
    }
  }
  double ans;
  ans = (double)BAZ / (double)QUZ;
  printf("%.6lf", ans);
  return 0;
}
