X = int(input())
Y = int(input())
L = int(input())
count = 0

# 方向転換の回数
if X == 0 and Y >= 0:
    pass
elif  X != 0 and Y >= 0:
    count += 1
else:
    count += 2

# 前進命令の回数
for i in [abs(X),abs(Y)]:
    if i == 0:
        pass
    elif i % L != 0:
        count += (i // L + 1)
    else:
        count += (i // L)
print(count)