We have a board with H horizontal rows and W vertical columns of squares. There is a bishop at the top-left square on this board. How many squares can this bishop reach by zero or more movements?  Here the bishop can only move diagonally. More formally, the bishop can move from the square at the r_1-th row (from the top) and the c_1-th column (from the left) to the square at the r_2-th row and the c_2-th column if and only if exactly one of the following holds:    * r_1 + c_1 = r_2 + c_2   * r_1 - c_1 = r_2 - c_2  For example, in the following figure, the bishop can move to any of the red squares in one move:  
h,w = map(int,input().split())
if w % 2 == 0:
    ans = h * w // 2
else:
    ans = (w//2) * h + (h//2)+1
print(ans)
from math import ceil
h,w = map(int,input().split())
ans = h * (w // 2)
if w % 2 != 0 :
    ans += ceil(h/2)
if h == 1 or w == 1:
    ans = 1
print(ans)