#include <iostream>
#include <vector>
#include <string>
#include <cstring>
#include <math.h>
#include <cmath>
#include <limits.h>
#include <map>
#include <set>
#include <queue>
#include <algorithm>
#include <functional>
#include <stdio.h>
using namespace std;

long long MOD = 1000000007;

double sum = 0;
int P,C;
int p[6] = { 2,3,5,7,11,13 };
int c[6] = { 4,6,8,9,10,12 };

void func( long long a, int d ) {
    
    if ( d == 0 ) {
        sum += a;
        return;
    }
    
    if ( d > C ) {
        for ( int i = 0; i < 6; i++ ) {
            func( a*p[i], d-1 );
        }
    }
    else {
        for ( int i = 0; i < 6; i++ ) {
            func( a*c[i], d-1 );
        }
    }
    
    
}


int main() {
    
    cin >> P >> C;
    
    func( 1, P+C );
    
    printf( "%.9f", sum / pow(6.0,P+C) );
    
    return 0;
}