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

int calc(int n, int m) {
	assert(n <= m);
	
	int s = n / 3, f = n / 3; // # of one-person seats, # of flights
	if (n % 3 != 0) {
		f++;
		s += 1 + (3 - n % 3) * 2;
	}
	
	if (s >= m - n) {
		return f * 2 - 1;
	}
	
	f += (m - n - s) / 4 + ((m - n - s) % 4 != 0);
	return f * 2 - 1;
}

int main() {
	int n, m;
	cin >> n >> m;
	if (n > m) {
		swap(n, m);
	}
	
	int ans = 1e9;
	for (int i = 0; i <= n; ++i) {
		ans = min(ans, calc(n - i, m + i));
	}
	cout << ans << endl;
	return 0;
}