from fileinput import input


data = input()

n, m = map(int, next(data).split())

if n == 1:
    if m == 1:
        print(0)
    else:
        print(m - 1)
else:
    if m == 1:
        print(n - 1)
    else:
        print((n - 1) + n * (m - 1))