from itertools import combinations
N,M = list(map(int,input().split()))

if(N%2 == 0):
    print(M*N)
else:
    # のこりの3つで最大化
    A = [0,0,0]
    for i in range(30,-1,-1):
        if(A[1] + (1<<i) > M):continue
        A[0] += 1<<i
        A[1] += 1<<i
        A.sort()
    print(M*(N-3) + sum(A))