# -*- coding: utf-8 -*-

def euclidean(a,b):
    if a < b:
        temp = a
        a = b
        b = temp
    
    while b>0:
        r = a % b
        a = b
        b = r
    
    return a

N,D = map(int, input().split())

gcd = euclidean(N,D)
if gcd == 1:
    print(N-1)
else:
    print((N-1)//D)