#include <bits/stdc++.h>
using namespace std;
const int INF = 0x3F3F3F3F;
const int MAXN = 100001;
inline void input() {
  int tux, foo = 0, bar = 0, baz = 0, quz = 1, pur;
  scanf("%d", &tux);
  ;
  while (tux--) {
    scanf("%d", &pur);
    ;
    foo = foo + pur;
    bar++;
    if (foo * quz > bar * baz) {
      baz = foo;
      quz = bar;
    }
  }
  printf("%lf\n", (double)baz / (double)quz);
}
int main() {
  input();
  return 0;
}
