import std.stdio;
import std.conv;
import std.random;
import std.algorithm;

int taro(int n, int k){
	int arr;
	foreach(i; 0..k){ arr += [4, 4, 5, 5, 6, 6][uniform(0, 6)]; }
	foreach(i; k..n){ arr += [1, 2, 3, 4, 5, 6][uniform(0, 6)]; }
	return arr;
}

int jiro(int n){
	int arr;
	foreach(i; 0..n){ arr += [1, 2, 3, 4, 5, 6][uniform(0, 6)]; }
	return arr;
}

void main(){
	int n, k; readf("%d\n%d", &n, &k);
	int win = 0;
	int times = 1000000;
	foreach(t; 0..times){
		if(taro(n, k) > jiro(n)) win++;
	}
	writeln(cast(real) win/times);
}