#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <cmath>
#include <string>
#include <vector>
#include <algorithm>
#include <queue>
#include <map>
#include <functional>
#include <set>
#include <numeric>
#include <stack>
#include <utility>
//#include "util.h"

using namespace std;
typedef long long lint;
typedef pair<lint, lint> Pii;

#define PI 3.14159265358979323846
#define EPS 1e-6
#define MOD ((lint)1000000007)
#define MIN(a,b) ((a)<(b)?(a):(b))
#define MAX(a,b) ((a)>(b)?(a):(b))

int main()
{
	int a, b, r, k;
	cin >> a >> b >> r;
	k = MAX(-a - b, MAX(a + b, MAX(-a + b, a - b)));
	for (; 2 * r * r >= MIN((a + b + k) * (a + b + k), MIN((-a - b + k)*(-a - b + k), MIN((a - b + k)*(a - b + k), (-a + b + k)*(-a + b + k)))); k++);
	cout << k << endl;

	return 0;
}