X = int(raw_input())
Y = int(raw_input())
L = int(raw_input())

ans = 0

def susumu(N):
    if N%L == 0:
        return N/L
    else:
        return N/L +1

if Y >= 0:
    ans += susumu(Y)
else:
    ans += susumu(-Y)+2

if X > 0:
    ans += susumu(X)+1
elif X < 0:
    ans += susumu(-X)+1
else:
    ans += susumu(X) # 0

print ans