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)
elif Y < 0:
    ans += susumu(-Y)

#print "Y", ans

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

#print "Y+X", ans

if X == 0 and Y == 0:
    ans = 0
elif Y >= 0 and X != 0:
    ans += 1
elif X == 0 and Y > 0:
    ans += 0
else:
    ans += 2

print ans