
H , W = input().split()
W = int(W)
H = int(H)
ans = int(0)

#Wが偶数なら(W//2)*H
#W.Hが奇数なら((W+1)//2)*((H+1)//2) + ((W - 1)//2*(H - 1)//2)
#Wが奇数Hが偶数(W+1)//2*(H//2) + ((W - 1)//2)*(H//2)

if(W == 1 or H == 1):
    ans = 1
elif(W%2 == 0):
    ans = (W//2)*H
elif(W%2 == 1 and H%2==1):
    ans = (((W+1)//2)*((H+1)//2)) + (((W - 1)//2)*((H - 1)//2))
elif(W%2 == 1 and H%2 ==0):
    ans = (((W+1)//2)*(H//2)) + (((W - 1)//2)*(H//2))
print(ans)