#include <stdio.h>
int main() {
  int sum = 0, cnt = 0;
  for (int i = 0, a; i < 10; i++) {
    scanf("%d", &a);
    if (a > 0) {
      sum += a;
      cnt++;
    }
  }
  printf("%.10f\n", (double)sum / cnt);
}