#include<iostream>

int main() {
	int n, k;

	std::cin >> n >> k;

	if (k == 1) {
		std::cout << 0 << std::endl;
		return 0;
	}

	long long start = 1;
	long long sum = 1;

	for (int i = 1; i < n - k + 1 ; i++) {
		sum += start;
		start = start * 2;
	}

	std::cout << sum << std::endl;
	
	return 0;
}