#include <bits/stdc++.h>
using namespace std;
typedef signed long long ll;

#define _P(...) (void)printf(__VA_ARGS__)
#define FOR(x,to) for(x=0;x<(to);x++)
#define FORR(x,arr) for(auto& x:arr)
#define FORR2(x,y,arr) for(auto& [x,y]:arr)
#define ALL(a) (a.begin()),(a.end())
#define ZERO(a) memset(a,0,sizeof(a))
#define MINUS(a) memset(a,0xff,sizeof(a))
template<class T> bool chmax(T &a, const T &b) { if(a<b){a=b;return 1;}return 0;}
template<class T> bool chmin(T &a, const T &b) { if(a>b){a=b;return 1;}return 0;}
//-------------------------------------------------------

ll N,M;

void solve() {
	int i,j,k,l,r,x,y; string s;
	
	cin>>N>>M;
	ll ret;
	if(N%2==0) {
		ret=N*M;
	}
	else {
		ret=(N-1)*M;
		if(N>=3) {
			ll tmp=(N-3)*M;
			vector<int> V;
			FOR(i,30) if(M&(1<<i)) V.push_back(1<<i);
			reverse(ALL(V));
			if(V.size()>=2) {
				tmp+=V[0]*2+(1LL*V[1]*2-1)*2;
			}
			ret=max(ret,tmp);
		}
	}
	cout<<ret<<endl;
}


int main(int argc,char** argv){
	string s;int i;
	if(argc==1) ios::sync_with_stdio(false), cin.tie(0);
	FOR(i,argc-1) s+=argv[i+1],s+='\n'; FOR(i,s.size()) ungetc(s[s.size()-1-i],stdin);
	cout.tie(0); solve(); return 0;
}