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

count = 0

if X == 0 and Y == 0:
    count = 0

elif Y > 0:
    count += (Y-1) // L + 1
    if X != 0:
        count += 1
        count += (abs(X)-1) // L + 1

else:
    count += 1
    if X != 0:
        count += (abs(X)-1) // L + 1
    if Y != 0:
        count += 1
        count += (abs(Y)-1) // L + 1

print(count)