/**
 * Tittle:	10081 - Tight Words
 * Author:	Cheng-Shih, Wong
 * Date:	2015/03/18
 */

// include files
#include <iostream>
#include <cstdio>
#include <cstring>

using namespace std;

// definitions
#define FOR(i,a,b) for( int i=(a),_n=(b); i<=_n; ++i )
#define clr(x,v) memset( x, v, sizeof(x) )
#define cur(x) ((x)&1)
#define pre(x) (((x)-1)&1)

// declarations
double dp[2][10];

// functions
int k, n;
double ans;

// main function
int main( void )
{
	double d;

	// input
	while( scanf( "%d%d", &k, &n )==2 ) {
		// solve
		clr( dp, 0 );
		d = k+1.0;
		FOR( i, 0, k ) dp[0][i] = 1/d;

		FOR( i, 1, n-1 ) {
			clr( dp[cur(i)], 0 );
			FOR( j, 0, k ) {
				if( j > 0 ) dp[cur(i)][j] += dp[pre(i)][j-1];
				dp[cur(i)][j] += dp[pre(i)][j];
				if( j < k ) dp[cur(i)][j] += dp[pre(i)][j+1];

				dp[cur(i)][j] *= 1/d;
			}
		}

		ans = 0;
		FOR( i, 0, k ) ans += dp[cur(n-1)][i];

		// output
		printf( "%.5lf\n", ans*100 );
	}

	return 0;
}