# Enter your code here. Read input from STDIN. Print output to STDOUT
def yo(n,m):
    if n*m==1:
        return 0
    if n>m:
        return 1+yo(n-1,m)+yo(1,m)
    else:
        return 1+yo(n,m-1)+yo(n,1)
n,m=map(int,raw_input().split())
print yo(n,m)