panasonic2020b.cpp

#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (n); i++)
#define rep2(i,s,n) for(int i = (s); i < (n); i++)
using namespace std;
using ll = long long;
using P = pair<int, int>;
int main(){
    ll h, w;
    cin >> h >> w;
    if(h==1||w==1){
        cout << 1 << endl;
    }else{
        cout << (h * w + 1) / 2 << endl;
    }
    return 0;
}