def pyon(N, D):
    ashiba = [x for x in range(1, N + 1)]
    loc = 0
    cnt = 0
    for i in range(N):
        ashiba[loc] = 0
        loc += D
        if loc > N - 1:
            loc -= N
        if ashiba[loc] == 0:
            break
        else:
            cnt += 1
    return cnt

def main():
    N, D = map(int, input().split())
    print(pyon(N, D))

if __name__ == '__main__':
    main()