#include <iostream>
#include <cstdio>
#include <vector>
#include <algorithm>
#include <utility>
#include <string>

using namespace std;

void check(int n, int k) {
	vector<int> a(n);
	for (int i = 0; i < n; i++) {
		a[i] = i + 1;
	}

	do {
		if (a[0] != k) {
			continue;
		}
		int n_big = 0;
		for (int i = 1; i < n; i++) {
			if (a[i - 1] > a[i]) {
				n_big++;
			}
		}
		if (n_big == 1) {
			for (auto e : a) {
				cout << e << " ";
			}
			cout << endl;
		}
	} while (next_permutation(a.begin(), a.end()));
 }

int main() {
	int n, k;
	// check(5,1);
	// return 0;

	cin >> n >> k;
	long long ans = 0;

	if (k == 1) {
		// 1 ??? 5 ??? -> 2^3 - 1
		// 1 ?? 4 ?? 5 -> 2^2 - 1
		for (int i = n - 2; i >= 0; i--) {
			ans += (1LL << i) - 1;
		}
	} else {
		ans = 1LL << (n - k);
	}

	cout << ans << endl;
	return 0;
}