#include<bits/stdc++.h>
typedef long long int ll;
typedef unsigned long long int ull;
#define BIG_NUM 2000000000
#define HUGE_NUM 4000000000000000000 //オーバーフローに注意
#define MOD 1000000007
#define EPS 0.000000001
using namespace std;




ll NUM = 10000;

ll input(){

	double tmp;
	scanf("%lf",&tmp);

	tmp *= NUM;

	return round(tmp);
}

bool ok(ll dx, ll dy, ll z){

	return dx*dx + dy*dy <= z*z;
}



int main(){

	ll x = input();
	ll y = input();
	ll z = input();

	x %= NUM;
	y %= NUM;

	ll L = 0,R = 1;

	ll ans = 0;

	//上半分
	for(ll h = BIG_NUM/2+5*NUM; h >= NUM; h -= NUM){

		while(ok(x-L*NUM,h-y,z))L--;
		while(ok(R*NUM-x,h-y,z))R++;

		ans += (R-L)-1;
	}

	L = 0,R = 1;

	//下半分
	for(ll h = -BIG_NUM/2-NUM; h <= 0; h += NUM){

		while(ok(x-L*NUM,y-h,z))L--;
		while(ok(R*NUM-x,y-h,z))R++;

		ans += (R-L)-1;
	}


	printf("%lld\n",ans);

	return 0;
}

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll, ll> P;
#define rep(i, n) for (ll i = 0; i < (ll)(n); ++i)
#define rep2(i, s, n) for (ll i = (s); i < (ll)(n); i++)
const ll MAX = 1001001;
const ll MOD = 1000000007;
const double pi = 2.0 * asin(1.0);
ll dx[4] = {1, 0, -1, 0};
ll dy[4] = {0, 1, 0, -1};
int main()
{
    long double x, y, r;
    cin >> x >> y >> r;
    x = abs(x);
    y = abs(y);
    x -= (ll)x / 1;
    y -= (ll)y / 1;
    ll d = (ll)(y - r);
    ll u = (ll)(y + r);
    ll ans = 0;
    rep2(i, d - 1, u + 1)
    {
        if (abs(i - y) > r)
        {
            continue;
        }
        long double now2 = r * r - (y - i) * (y - i);
        long double l = 0;
        long double l2 = 1001001001;
        rep(i, 100)
        {
            long double mid = (l + l2) / 2;
            if (mid * mid > now2)
            {
                l2 = mid;
            }
            else
            {
                l = mid;
            }
        }
        ans += (ll)l * 2 + 1;
        long double x1 = (ll)l + 1;
        long double x2 = -(ll)l;
        long double eps = 0.0000000001;
        if ((i - y) * (i - y) + (x1 - x) * (x1 - x) <= r * r + eps)
        {
            ans++;
        }
        if ((i - y) * (i - y) + (x2 - x) * (x2 - x) > r * r + eps)
        {
            ans--;
        }
    }
    cout << ans << endl;
}