#include <bits/stdc++.h>
int max(int a, int b) { return a > b ? a : b; }
int main() {
  int tux;
  scanf("%d", &tux);
  int foo = 0;
  int bar = 0;
  int baz = 0;
  int quz = 1;
  for (; tux--;) {
    int pur;
    scanf("%d", &pur);
    foo += pur;
    bar += 1;
    if (max(foo * quz, bar * baz) == foo * quz) {
      baz = foo;
      quz = bar;
    }
  }
  printf("%lf\n", ((double)baz) / quz);
  return 0;
}
