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

#define rep(i,n) for(int i = 0; i < n; ++i)
using ll = long long;

int main(void) {
    ll N, M;
    cin >> N >> M;
    
    if(N % 2 == 0) {
    	cout << N * M << endl;
    	return 0;
    }
    
    if(N == 1) {
    	cout << 0 << endl;
    	return 0;
    }
    
    ll cnt = 0;
    rep(i,60) {
    	if((M >> i) == 0) break;
    	if((M >> i & 1) == 0) cnt += (1LL << i);
    }
    
    cout << (N - 1) * M + cnt * 2 << endl;
    
    return 0;
}