X=int(raw_input())
Y=int(raw_input())
L=int(raw_input())
if Y<0: r=2
elif X==0: r=0
else: r=1
X=abs(X)
Y=abs(Y)
x=X/L if X%L==0 else X/L+1
y=Y/L if Y%L==0 else Y/L+1
print x+y+r