N,B=map(int,input().split())
if (N-1)%2==0:
    print((N-1)//2)
    exit()
from math import gcd
try:
    x=gcd(N-1,B)
    B//=x
    result=((N-1)//x)*pow(2,-1,B)
    result%=B
    print(result)
except:
    print('NaN')