#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
extern int getchar_unlocked(void);
extern int putchar_unlocked(int);
#define DEBUGe
// ---------------------------
#define NOP do{}while(0)
#define gc(d)	(d)=getchar_unlocked()
#define pc(d)	putchar_unlocked(d)
#define mygc(c)	(c)=getchar()
#define PRINCR	pc('\n')
#ifdef DEBUG
#include <time.h>
#define TRACE(...) do{fprintf(stderr,__VA_ARGS__);}while(0)
#define TRACECR do{fprintf(stderr,"\n");}while(0)
static clock_t	startclock;
void DEBUGSTART(void){TRACE("--DEBUG MODE --\n");startclock=clock();}
void DEBUGEND(void){startclock=clock()-startclock;TRACE("--finish --\ntime is %.3fms\n",startclock/1000.);}
#else
#define TRACE(...) NOP
#define TRACECR NOP
void DEBUGSTART(void){return;}
void DEBUGEND(void){return;}
#endif
// ---------------------------
#define NOCR(strig) do{char *p;p=strchr(strig,'\n');if(p)*p='\0';}while(0)
#define SWAP(type,a,b) do{type _c;_c=a;a=b;b=_c;}while(0)
#define MAX(a,b)	((a)>(b)?(a):(b))
#define MID(a,b,c)	((a)>(b)?(b)>(c)?(b):(a)>(c)?(c):(a):(c)>(b)?(b):(c)>(a)?(c):(a))
#define MIN(a,b)	((a)<(b)?(a):(b))
#define REP(a,b)	for(int a=0;a<(int)(b);++a)
#define REP1(a,b)	for(int a=1;a<=(int)(b);++a)
#define ll	long long
#define INPUT	GETLINE
#define	ull	unsigned ll
#define	ui	unsigned int
static char *GETWORD(char* str) {char c;char *cp;cp=&str[0];gc(c);while(c!=EOF){if((c==' ')||(c=='\n'))break;*cp++=c;gc(c);}*cp='\0';return &str[0];}
#define GETLINE(str) do{char *p;fgets(str,sizeof(str),stdin);p=strchr(str,'\n');if(p)*p='\0';}while(0)
#define REP(a,b) for(int a=0;a<(int)(b);++a)
static int GETLINEINT(void) {char s[34];GETLINE(s);return atoi(s);}
static int GETWORDINT(void) {char s[34];GETWORD(s);return atoi(s);}
static ll GETWORDLL(void) {char s[34];GETWORD(s);return atoll(s);}
static long GETLINELONG(void) {char s[34];GETLINE(s);return atol(s);}
static ll GETLINELL(void) {char s[34];GETLINE(s);return atoll(s);}
static int cmpint123(const void *a,const void *b){if(*(int *)a>*(int *)b){return 1;}if(*(int *)a==*(int *)b){return 0;}return -1;}
static int cmpint321(const void *a,const void *b){if(*(int *)a<*(int *)b){return 1;}if(*(int *)a==*(int *)b){return 0;}return -1;}
static ll midll(ll a,ll b,ll c){if(a>b){if(b>c){return b;}else if(a>c){return c;}
else{return a;}}else{if(c>b){return b;}else if(c>a){return c;}else{return a;}}}
static int gcd(int a,int b){int c;while(b!=0){c=a%b;a=b;b=c;}return a;}    // 最大公約数
static ll gcdll(ll a,ll b){ll c;while(b!=0){c=a%b;a=b;b=c;}return a;}    // 最大公約数
#define Yes(a)    printf("%s\n",((a)?"Yes":"No"))
// ---------------------------
// グローバル変数
//	[1][0] = 15/36;
//	[1][1] = 24/36;
#define DMAX	(6*10)
int N,K;
ll win = 0;
double	wk[(DMAX+12)];
double	dp123456[(DMAX+12)];
double	dp445566[(DMAX+12)];
// ---------------------------
void read(void)
{
	N = GETLINEINT();
	K = GETLINEINT();
}
void init(void)
{
	REP1(i,DMAX) dp123456[i] = 0.;
	REP1(i,DMAX) dp445566[i] = 0.;
}
// *********************
int main( void )
{
	double ans = 0;

	init();
	read();
	
	DEBUGSTART();
	TRACE("N%2d,K%2d\n",N,K);
	dp123456[0] = 1.;
	REP(m,N) {
		REP(i,DMAX) wk[i] = 0.;
		for(int k = 0; k <= DMAX-6 ; k++) {
			double pls = dp123456[k]/6.;
			REP1(i,6) {
				wk[k+i] += pls;
			}
		}
		memcpy( dp123456, wk , sizeof(wk[0]) * (DMAX+12) );
	}
	REP1(m,13) TRACE("%2d-%.9f\n",m,dp123456[m]);
	dp123456[0] = 0.;
	dp445566[0] = 1.;
	REP(m,K) {
		REP(i,DMAX) wk[i] = 0.;
		for(int k = 0; k <= DMAX-6 ; k++) {
			double pls = dp445566[k]/3.;
			for(int i=4; i<=6;i++) {
				wk[k+i] += pls;
			}
		}
		memcpy( dp445566, wk , sizeof(wk[0]) * (DMAX+12) );
	}
	REP(m,N-K) {
		REP(i,DMAX) wk[i] = 0.;
		for(int k = 0; k <= DMAX-6 ; k++) {
			double pls = dp445566[k]/6.;
			REP1(i,6) {
				wk[k+i] += pls;
			}
		}
		memcpy( dp445566, wk , sizeof(wk[0]) * (DMAX+12) );
	}
	dp445566[0] = 0.;
	REP1(m,37) TRACE("%2d-%.9f\n",m,dp445566[m]);
	REP(i,DMAX) for(int k=i+1; k <= DMAX;k++) ans += dp123456[i] * dp445566[k];
	printf("%.15f\n",ans );
	DEBUGEND();
}