x, y, r = map(int, input().split())
x = abs(x)
y = abs(y)

# k 乗根
def sqrt(n: int, k = 2):
    l = k - 1
    if not n: return 0
    y = 1 << (n.bit_length() + l) // k
    x = y + 1
    while y < x:
        x = y
        y = (l * x + n // (x ** l)) // k
    return x

# 平方数の判定
def issquare(n):
    x = sqrt(n, 2)
    return x*x == n

def f(n):
    if issquare(n):
        return sqrt(n)
    else:
        return sqrt(n) + 1

ans = f(2*r*r) + x + y
print(ans)