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

x = (abs(X)+L-1)//L
y = (abs(Y)+L-1)//L
if 0 <= Y and X == 0:
    count = y    
elif 0 <= Y and X != 0:
    count = x + y + 1
elif Y < 0:
    count = x + y + 2
print(count)