#include <iostream>
#include <algorithm>
#include <cstdlib>
using namespace std;
#define E 1000000
int main(){
	int n,k;	cin>>n>>k;
	int cnt=0;
	for(int i=0;i<E;i++){
		int taro=0,jiro=0;
		for(int j=0;j<n;j++){
			jiro+=(rand()%6)+1;
		}
		for(int j=0;j<k;j++){
			taro+=(rand()%3)+4;
		}
		for(int j=k;j<n;j++){
			taro+=(rand()%6)+1;
		}
		if(taro>jiro)	cnt++;
	}
	cout<<(double)cnt/E<<endl;
	return 0;
}