#include <bits/stdc++.h>
int main() {
  int TUX, FOO = 0, BAR = 0, BAZ = 0, QUZ = 1;
  double result;
  scanf("%d", &TUX);
  while (TUX--) {
    int PUR;
    scanf("%d", &PUR);
    FOO += PUR;
    BAR += 1;
    if (FOO * QUZ >= BAR * BAZ) {
      BAZ = FOO;
      QUZ = BAR;
    }
  }
  result = 1. * BAZ / QUZ;
  printf("%lf", result);
  return 0;
}
