from math import ceil

def abs_ceil(l):
    def _(n):
        return abs(ceil(n / l))
    return _

X,Y,L = map(int,[input() for x in range(3)])
command = 0
abceil = abs_ceil(L)
if Y < 0:
    command+=2
elif X:
    command+=1
command+=abceil(X) + abceil(Y)
print(command)