#include <bits/stdc++.h>

using namespace std;

int main(void) {
  int x, y, r;
  cin >> x >> y >> r;
  x = abs(x); y = abs(y);

  for (int i = x + r; ; i++) {
    if ((i - x) * (i - x) <= 2 * r * r) continue;
    cout << y + i << endl;
    break;
  }

  return 0;
}