def pyon(N, D):
    if N == D:
        return 0
    while True:
        a = N % D
        if a == 1:
            break
        elif a == 0:
            N = N // D
            D = 1
            break
        elif (N % a == 0) and (D % a == 0):
            N = N // a
            D = D // a
        else:
            break
    return N - 1

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

if __name__ == '__main__':
    main()