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

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    
    long long N,M; cin >> N >> M;
    if(N%2 == 0){cout << N*M << endl; return 0;}
    long long answer = N/2*2*M,now = (N-2)*M;
    for(int i=30; i>=0; i--) if(M&(1<<i)){
        int mask = (1<<i)-1;
        now += (1LL<<i)+(mask&(~M));
        now += mask;
        break;
    }
    cout << max(answer,now) << endl;
}