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

typedef long long int int64;

#define MAX(a,b) ((a)>(b)?(a):(b))
#define MIN(a,b) ((a)<(b)?(a):(b))
#define ABS(a) ((a)>(0)?(a):-(a))

void run(void){
  int n;
  scanf("%d",&n);
  const int f=6;
  const double p=(double)1/f;
  double *now=(double *)calloc(f+1,sizeof(double));
  now[1]=1;
  double *next=(double *)calloc(f+1,sizeof(double));
  int i;
  for(i=2;i<=n;i++){
    int j;
    for(j=1;j<=f;j++){
      next[j]=now[j]*(j*p)+now[j-1]*((f-(j-1))*p);
    }
    double *swap=now;
    now=next;
    next=swap;
  }
  printf("%.9lf\n",now[f]);
}

int main(void){
  run();
  return 0;
}