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

if X == 0 and Y == 0:
    print(0)
elif X == 0 and Y > 0:
    N = -(-Y//L)
    print(N)
elif X > 0 and Y == 0:
    N = -(-X//L) + 1
    print(N)
elif X == 0 and Y < 0:
    N = -(-abs(Y)//L) + 2
    print(N)
elif X > 0 and Y > 0:
    N = -(-X//L) - (-Y//L) + 1
    print(N)
elif X < 0 and Y > 0:
    N = -(-abs(X)//L) - (-Y//L) + 1
    print(N)
elif X < 0 and Y < 0:
    N = -(-abs(X)//L) - (-abs(Y)//L) + 2
    print(N)
elif X > 0 and Y < 0:
    N = -(-X//L) - (-abs(Y)//L) + 2
    print(N)