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