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

count = 0
if Y < 0:
    count += 2
elif X != 0:
    count += 1

y = abs(Y)
count += y // L if y % L == 0 else y//L + 1
count += X // L if X % L == 0 else X//L + 1

print(count)