#include <stdio.h>

#define	DMAX	(11)
#define SMAX	(130)
int nDice[DMAX+2][SMAX];
int tDice[DMAX+2][SMAX];

int normalDice[] = {1,2,3,4,5,6};
int trickDice[] = {4,5,6,4,5,6};
long long int yourDice[SMAX], sum;


int main(void){
	int i,j,k;
	int N,K;
	double dsum;
	
	scanf("%d", &N);
	scanf("%d", &K);
	
	nDice[0][0] = 1;
	tDice[0][0] = 1;
	
	
	for(i=1;i<=DMAX;i++){
		for(k=i-1;k<SMAX;k++){
			for(j=0;j<6;j++){
				int eyeA = normalDice[j];
				int eyeB = trickDice[j];
				if(nDice[i-1][k] != 0){
					nDice[i][k+eyeA] += nDice[i-1][k];
				}
				
				if(tDice[i-1][k] != 0){
					tDice[i][k+eyeB] += tDice[i-1][k];
				}
				
			}
		}
	}
	
	for(i=0;i<SMAX;i++){ // normalDice
		if(nDice[(N-K)][i] == 0){continue;}
		
		for(j=0;j<SMAX;j++){ // trickDice
			if(tDice[K][j] != 0){
				yourDice[i+j] = yourDice[i+j]+nDice[(N-K)][i] * tDice[K][j];
			}
		}
	}
	
	
	
	for(i=0;i<SMAX;i++){ // trickDice
		if(yourDice[i] == 0){continue;}
		for(j=0;j<i;j++){ // normalDice
			sum += nDice[N][j] * yourDice[i];
		}
	}
	
	dsum = 1.0*sum;
	for(i=0;i<N;i++){
		dsum/=6;
	}
	for(i=0;i<N;i++){
		dsum/=6;
	}
	
	printf("%.6f\n", dsum);
	return 0;
}