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

typedef long long ll;

const long long MOD = 1000000007;
long long modpow(long long a, long long n, long long m)
{
    long long ans = 1;
    while (n)
    {
        if (n & 1)
        {
            ans = (ans * a) % m;
        }
        a = (a * a) % m;
        n >>= 1;
    }
    return ans;
}
long long combi(long long n, long long a)
{
    long long ans = 1, ans1 = 1;
    for (long long i = n - a + 1; i <= n; i++)
    {
        ans *= i % MOD;
        ans %= MOD;
    }

    for (long long i = 2; i <= a; i++)
        ans1 = (ans1 * i) % MOD;
    ans1 = modpow(ans1, MOD - 2, MOD);
    return ((ans % MOD) * ans1) % MOD;
}

int main()
{

    ll H, W;
    cin >> H >> W;

    bool f = true;
    ll ans = 0;

    if (H % 2 == 0)
    {
        cout << (floor(W / 2) + 1) * (H / 2) + (floor(W / 2)) * (H / 2) << endl;
    }
    else
    {
        ll tmp = ceil(H / 2) + 1;
        ll a = (floor(W / 2) + 1) * tmp;
        ll b = (floor(W / 2) * floor(H / 2));
        cout << a + b << endl;
    }
    return 0;
}
