#include <bits/stdc++.h>
using namespace std;

const int A = 1000000000;

void read(long long &x) {
  double s;
  cin >> s;
  x = round(s * 10000);
}

long long sqrtll(long long x) {
  long long l = 0, r = A;
  while (l < r) {
    long long m = (l + r + 1) / 2;
    if (m * m <= x) {
      l = m;
    } else {
      r = m - 1;
    }
  }
  return r;
}

long long floor_div(long long x, long long y) {
  return x / y - (x % y < 0);
}

long long ceil_div(long long x, long long y) {
  return x / y + (x % y > 0);
}

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);

  long long x, y, r;
  read(x), read(y), read(r);

  long long ans = 0;
  for (long long i = -2 * A; i <= 2 * A; i += 10000) {
    long long s = r * r - (x - i) * (x - i);
    if (s < 0) {
      continue;
    }
    s = sqrtll(s);
    ans += floor_div(y + s, 10000) - ceil_div(y - s, 10000) + 1;
  }

  cout << ans << "\n";
}

#include <bits/stdc++.h>
#define lli long long int
#define pb push_back
#define mod 1000000007
#define inf 1000000000000000000
#define mp make_pair
using namespace std;
int main()
{
    cout.precision(16);
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
    long double x,y,r;
    cin>>x>>y>>r;
    lli start=ceil(x-r), rear=floor(x+r), ans=0;
    for(lli i=start; i<=rear; i++)
    {
        long double z=y+sqrt(r*r-(i-x)*(i-x)+1e-9);
        long double l=y-sqrt(r*r-(i-x)*(i-x)+1e-9);
        ans+=(floor(z)-ceil(l)+1);
    }
    cout<<ans;
    return 0;
}