H,W = map(int, input().split())


h = 0
w = 0
w1 = w2 = 0
if W % 2 == 1:#横が奇数
    w = int(W /2) + 1
    if H % 2 == 1:#縦が奇数
        h = int(H / 2) + 1
        w1 = h * w
        w2 = (w-1) * (h-1)
        print(w1 + w2)
    else:#縦が偶数
        h = int(H / 2)
        w1 = w * h
        w2 = (w-1) * h
        print(w1 + w2)
        
        
else:#横が偶数
    w = int(W / 2)
    print(w * H)
