#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std;
signed main () {
  std::ios::sync_with_stdio(false); std::cin.tie(0);
  long double inx, iny, inr;
  cin >> inx >> iny >> inr;
  long double x = inx + 200005, y = iny + 200005, r = inr;
  long long ans = 0;
  for (long double p = ceil(x - r); p <= floor(x + r); p += 1) {
    long double d = x - p;
    long double h = sqrtl(r * r - d * d);
    long long top = floor(y + h);
    long long bottom = ceil(y - h);
    ans += top - bottom + 1;
  } 
  cout << ans << endl;
}

#pragma GCC target("avx2")
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>
//#include <atcoder/all>
using namespace std;
//using namespace atcoder;
#define DEBUG
#ifdef DEBUG
template <class T, class U>
ostream &operator<<(ostream &os, const pair<T, U> &p) {
    os << '(' << p.first << ',' << p.second << ')';
    return os;
}
template <class T> ostream &operator<<(ostream &os, const vector<T> &v) {
    os << '{';
    for(int i = 0; i < (int)v.size(); i++) {
        if(i) { os << ','; }
        os << v[i];
    }
    os << '}';
    return os;
}
void debugg() { cerr << endl; }
template <class T, class... Args>
void debugg(const T &x, const Args &... args) {
    cerr << " " << x;
    debugg(args...);
}
#define debug(...)                                                             \
    cerr << __LINE__ << " [" << #__VA_ARGS__ << "]: ", debugg(__VA_ARGS__)
#define dump(x) cerr << __LINE__ << " " << #x << " = " << (x) << endl
#else
#define debug(...) (void(0))
#define dump(x) (void(0))
#endif
using namespace std;
typedef long long ll;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<char> vc;
typedef vector<string> vs;
typedef vector<bool> vb;
typedef vector<double> vd;
typedef pair<ll,ll> P;
typedef pair<int,int> pii;
typedef vector<P> vpl;
typedef tuple<ll,ll,ll> tapu;
#define rep(i,n) for(int i=0; i<(n); i++)
#define REP(i,a,b) for(int i=(a); i<(b); i++)
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
const int inf = 1<<30;
const ll linf = 1LL<<62;
const int MAX = 4020000;
int dy[8] = {0,1,0,-1,1,-1,-1,1};
int dx[8] = {-1,0,1,0,1,-1,1,-1};
const double pi = acos(-1);
const double eps = 1e-7;
template<typename T1,typename T2> inline bool chmin(T1 &a,T2 b){
	if(a>b){
		a = b; return true;
	}
	else return false;
}
template<typename T1,typename T2> inline bool chmax(T1 &a,T2 b){
	if(a<b){
		a = b; return true;
	}
	else return false;
}
template<typename T> inline void print(T &a){
    int sz = a.size();
    for(auto itr = a.begin(); itr != a.end(); itr++){
		cout << *itr;
        sz--;
        if(sz) cout << " ";
	}
    cout << "\n";
}
template<typename T1,typename T2> inline void print2(T1 a, T2 b){
	cout << a << " " << b << "\n";
}
template<typename T1,typename T2,typename T3> inline void print3(T1 a, T2 b, T3 c){
	cout << a << " " << b << " " << c << "\n";
}
void mark() {cout << "#" << "\n";}
ll pcount(ll x) {return __builtin_popcountll(x);}
const int mod = 1e9 + 7;
//const int mod = 998244353;

int main(){
    string X,Y,R; cin >> X >> Y >> R;
    ll x,y,r; //cin >> x >> y >> r;
    auto f = [](string s) -> ll{
        int cnt = 4;
        ll res = 0;
        bool f = false;
        for(auto c : s){
            cnt -= f;
            if(c == '-') continue;
            if(c != '.') res = res * 10 + c - '0';
            else f = true;
        }
        rep(i,cnt) res *= 10;
        if(s[0] == '-') res = -res;
        return res;
    };
    x = f(X);
    y = f(Y);
    r = f(R);
    x += 2000000000LL;
    ll ans = 0;
    for(ll i=-2000000000; i<=2000000000; i+=10000){
        if(y-r > i || y+r < i) continue;
        ll d = abs(y-i);
        ll ok = 0, ng = r+1;
        while(ng-ok > 1){
            ll mid = (ok+ng) / 2;
            if(mid*mid <= r*r-d*d) ok = mid;
            else ng = mid;
        }
        //debug(x,ok);
        ll p = (x-ok+9999) / 10000;
        ll q = (x+ok) / 10000;
        //debug(i,p,q);
        ans += q-p+1;
    }
    cout << ans << "\n";
}