#include <bits/stdc++.h>
using namespace std;

long long T[ 1000 ];
long long J[ 1000 ];
long long X[ 1000 ];
int iT;
int iJ;
int iEnd;
long long iSumT;
long long iSumJ;

int DiceJ( long long A[], const int iA, const int iEnd )
{
int i;
int j;
int iNewE;

	iNewE = iEnd + 6;
	for( i = iA; i < iEnd; i++ )		X[ i + 1 ] = A[ i ];
	for( i = iEnd + 1; i < iNewE; i++ )	X[ i ] = 0;

	for( i = iA; i < iEnd; i++ )
	{
		for( j = 2; j <= 6; j++ )
		{
			X[ i + j ] += A[ i ];
		}
	}
	
	A[ iA ] = 0;
	for( i = iA + 1; i < iNewE; i++ ) A[ i ] = X[ i ];
	
	return iA + 1;
}

int DiceT( long long A[], const int iA, const int iEnd )
{
int i;
int j;
int iNewE;

	iNewE = iEnd + 6;
	for( i = iA; i < iEnd; i++ )		X[ i + 4 ] = A[ i ];
	for( i = iEnd + 4; i < iNewE; i++ )	X[ i ] = 0;

	for( i = iA; i < iEnd; i++ )
	{
		for( j = 5; j <= 6; j++ )
		{
			X[ i + j ] += A[ i ];
		}
	}
	
	A[ iA ] = 0;
	A[ iA + 1 ] = 0;
	A[ iA + 2 ] = 0;
	A[ iA + 3 ] = 0;
	for( i = iA + 4; i < iNewE; i++ ) A[ i ] = X[ i ];
	
	return iA + 4;
}

int main()
{
int i;
int a;
int N;
int K;
long long iSum;
long long iAll;

	cin >> N;
	cin >> K;
	
	J[ 0 ] = 1;
	J[ 1 ] = 1;
	J[ 2 ] = 1;
	J[ 3 ] = 1;
	J[ 4 ] = 1;
	J[ 5 ] = 1;
	iJ = 0;
	iSumJ = 6;
	
	if( K > 0 )
	{
		T[ 0 ] = 0;
		T[ 1 ] = 0;
		T[ 2 ] = 0;
		T[ 3 ] = 1;
		T[ 4 ] = 1;
		T[ 5 ] = 1;
		iT = 3;
		iSumT = 3;
	}
	else
	{
		T[ 0 ] = 1;
		T[ 1 ] = 1;
		T[ 2 ] = 1;
		T[ 3 ] = 1;
		T[ 4 ] = 1;
		T[ 5 ] = 1;
		iT = 0;
		iSumT = 6;
	}

	iEnd = 6;
	for( i = 1; i < K; i++ )
	{
		DiceT( T, iT, iEnd );
		iT += 4;
		iEnd += 6;
		iSumT *= 3;
	}

	i = K;
	if( K == 0 ) i++;

	for(; i < N; i++ )
	{
		DiceJ( T, iT, iEnd );
		iT++;
		iEnd += 6;
		iSumT *= 6;
	}

	iEnd = 6;
	for( i = 1; i < N; i++ )
	{
		DiceJ( J, iJ, iEnd );
		iJ++;
		iEnd += 6;
		iSumJ *= 6;
	}


	X[ iEnd ] = 0;
	for( i = iEnd - 1; i >= 0; i-- )
	{
		X[ i ] = X[ i + 1 ] + T[ i ];
	}

	iAll = iSumT * iSumJ;
	
	iSum = 0;
	for( i = iJ; i < iEnd; i++ )
	{
		iSum += J[ i ] * X[ i + 1 ];
	}

	cout << (double) iSum / iAll << endl;

	return 0;
}