#include <bits/stdc++.h>

const long long base = 2000000000ll;
const long long ten[6] = {1ll, 10ll, 100ll, 1000ll, 10000ll, 100000ll};

using namespace std;

long long str2ll(string str) {
  long long ret = 0;
  
  bool fp = false;
  int f = 0;
  for (int i = 0; i < (int)str.size(); i++) {
    if (str[i] == '-') continue;
    else if (str[i] == '.') {
      fp = true;
      ret *= ten[4];
    } else if (fp) {
      ret += ten[3 - f] * (str[i] - '0');
      ++f;
    } else {
      ret *= 10;
      ret += str[i] - '0';
    }
  }
  
  if (!fp) ret *= ten[4];
  
  return ret;
}

long long sqroot(long long x) {
  long long ok = 0, ng = 2000000000ll;
  while (ng - ok > 1) {
    long long mid = (ok + ng) >> 1;
    
    (mid * mid <= x ? ok : ng) = mid;
  }
  return ok;
}

int main() {
  long long X, Y, R;
  
  string X_str, Y_str, R_str;
  cin >> X_str >> Y_str >> R_str;
  
  X = str2ll(X_str) + base;
  Y = str2ll(Y_str) + base;
  R = str2ll(R_str);
  
  long long ans = 0;
  for (long long x = (X - R) / ten[4] * ten[4] - ten[4]; x <= (X + R) / ten[4] * ten[4] + ten[4]; x += ten[4]) {
    if (R * R - (x - X) * (x - X) < 0) continue;
    
    long long s = sqroot(R * R - (x - X) * (x - X));
    ans += (Y + s) / ten[4] - (Y - s - 1) / ten[4];
  }
  
  cout << ans << endl;
  
  return 0;
}
#include <bits/stdc++.h>

#define fr first
#define sc second
#define mk make_pair
#define pb push_back
using namespace std;

typedef long long ll;
typedef long double ld;
typedef pair <int, int> pii;
typedef pair <ll, ll> pll;
const int inf = 1e9 + 7;
const int N = 1e6 + 5;

void solve() {
    ll b, c, ans = 1;
    cin >> b >> c;
    if (b != 0 && c > 0) ans ++;
    if (b < 0) {
        ans += c / 2;
        ans += (c - 1) / 2;
        ans += min(abs(b), (c - 1) / 2);
        ans += min(abs(b), (c - 2) / 2);
        if (abs(b) <= (c - 2) / 2) ans --;
    } else if (b == 0) {
        ans += c / 2;
        ans += (c - 1) / 2;
    } else {
        ans += min(b, c / 2);
        if ((c - 1) / 2 >= b) ans --;
        ans += min(b, (c - 1) / 2);
        ans += (c - 1) / 2;
        ans += (c - 2) / 2;
    }
    cout << ans << endl;
}

int main() {
    int tests = 1;
//    cin >> tests;
    while (tests --)
        solve();
    return 0;
}


