X = abs(int(input()))
Y = int(input())
L = int(input())
C = (X//L+1 if X%L!=0 else X//L) + (abs(Y)//L+1 if abs(Y)%L!=0 else abs(Y)//L)
if Y>=0 and X>0:C += 1
elif Y<0:C += 2
print(C)