import sys
input=lambda: sys.stdin.readline().rstrip()
x=int(input())
y=int(input())
l=int(input())
ans=0
if y>0:
  ans+=(y-1)//l+1
  if x==0:
    print(ans)
  else:
    ans+=1+(abs(x)-1)//l+1
    print(ans)
elif y<0:
  ans+=2+(abs(y)-1)//l+1
  if x==0:
    print(ans)
  else:
    ans+=(abs(x)-1)//l+1
    print(ans)
else:
  if x==0:
    print(ans)
  else:
    ans+=1+(abs(x)-1)//l+1
    print(ans)