#include <stdio.h>
#include <stdlib.h>

#define MAX 12

int rollProbability(int number) {
  int sum = 0;
  for (int i=1; i<=6; i++) {
    for (int j=1; j<=6; j++) {
      if (i+j == number) {
        sum++;
      }
    }
  }
  return sum;
}

int main(int argc, char **argv) {
  int hotels;
  int distances[MAX];

  scanf("%d", &hotels);

  float sum = 1/6;
  for (int i=0; i<hotels; i++) {
    scanf("%d", &distances[i]);
  }

  for (int i=0; i<hotels; i++) {
    sum += rollProbability(distances[i]) / 36.0;
  }

  printf("%f\n", sum);
  return 0;
}