import math
ans = 0
X = int(input())
Y = int(input())
L = int(input())
if Y >= 0 and X == 0:
    ans += math.ceil(Y/L)
elif Y >= 0 and X != 0:
    ans += math.ceil(Y/L) + math.ceil(abs(X)/L) + 1
elif Y < 0:
    ans += math.ceil(abs(Y)/L) + math.ceil(abs(X)/L) + 2

print(ans)