import math

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

# Expected value = (N - 1) / 2

if (N - 1) % 2 == 0:
    print(((N - 1) // 2) % B)
else:
    # denominator is 2, so inverse of 2 mod B must exist
    if math.gcd(2, B) != 1:
        print("NaN")
    else:
        inv2 = pow(2, -1, B)
        print((N - 1) * inv2 % B)