#include <bits/stdc++.h>
using namespace std;
int read() {
  int x = 0, f = 1;
  char c = getchar();
  while (c < '0' || c > '9') {
    if (c == '-') f = -1;
    c = getchar();
  }
  while (c >= '0' && c <= '9') {
    x = x * 10 + c - '0';
    c = getchar();
  }
  return x * f;
}
int main() {
  int n = read();
  int FOO = 0, BAR = 0, BAZ = 0, QUZ = 1;
  while (n--) {
    int PUR = read();
    FOO = FOO + PUR;
    BAR = BAR + 1;
    if (FOO * QUZ > BAZ * BAR) {
      BAZ = FOO;
      QUZ = BAR;
    }
  }
  printf("%lf", BAZ * 1.0 / QUZ);
  return 0;
}
