X = int(input())
Y = int(input())
L = int(input())

cnt = 0
if Y < 0:
    cnt += 2
    cnt += -(-abs(Y)//L)
    if X != 0:
        cnt += -(-abs(X)//L)
elif Y > 0:
    cnt += -(-Y//L)
    if X != 0:
        cnt += 1
        cnt += -(-abs(X)//L)
print(cnt)