#include <bits/stdc++.h>
using namespace std;

using ll = long long;

int main(void) {
	ll N, M;
	cin >> N >> M;
	
	if(N % 2 == 0) {
		cout << N * M << "\n";
		return 0;
	}
	
	vector<ll> v(3, 0);
	for(int i = 30; i >= 0; --i) {
		sort(v.begin(), v.end());
		if(v[1] + (1LL << i) <= M) {
			v[0] += (1LL << i);
			v[1] += (1LL << i);
		}
	}
	
	cout << v[0] + v[1] + v[2] + (N - 3) * M << "\n";
	
	return 0;
}