double dp[1<<20][9];i,j;
main(n){for(dp[1][1]=scanf("%d",&n);++i<n;)for(j=0;j++<6;)dp[i+1][j+1]+=dp[i][j]*(6-j)/6,dp[i+1][j]+=dp[i][j]*j/6;
	printf("%.9lf",dp[n][6]);
}