#include <stdio.h>

int p, c, j[10];

int main(void) {
	int n;
	scanf("%d%d", &p, &c);
	int a[6] = {2, 3, 5, 7, 11, 13};
	int b[6] = {4, 6, 8, 9, 10, 12};
	
	int i;
	double sum = 0;
	while(1) {
		double prod = 1; // intの最大 < (13*12)^5 なのでintには入らない
		for(i = 0; i < p    ; i++) { prod *= a[ j[i] ]; }
		for(i = p; i < p + c; i++) { prod *= b[ j[i] ]; }
		sum += prod;
		
		i = 0;
		while(j[i] == 5) {
			j[i] = 0;
			i++;
		}
		if(i == p + c) { break; }
		j[i]++;
	}
	
	int q = 1;
	for(i = 0; i < p + c; i++) { q *= 6; }
	
	printf("%.9f\n", sum / q );
	return 0;
}