#include <bits/stdc++.h>
using namespace std;
int main() {
  long long n, x, y, c;
  cin >> n >> y >> x >> c;
  long long now = 0;
  long long i, xr, xl, yu, yd, d;
  x--;
  y--;
  for (i = 1; now < c; i++) {
    now = i * i + (i - 1) * (i - 1);
    if (now < c) continue;
    i--;
    xr = x + i;
    xl = x - i;
    yu = y - i;
    yd = y + i;
    if (xl < 0) now -= xl * xl;
    if (xr > n - 1) now -= (xr - n + 1) * (xr - n + 1);
    if (yu < 0) {
      now -= yu * yu;
      yu++;
      d = -yu;
      if (x + d > n - 1) now += (x + d - n + 2) * (x + d - n + 1) / 2;
      if (x + yu < 0) now += (x - d) * (x - d - 1) / 2;
    }
    if (yd > n - 1) {
      now -= (yd - n + 1) * (yd - n + 1);
      d = yd - n + 1;
      d--;
      if (x + d > n - 1) now += (x + d - n + 2) * (x + d - n + 1) / 2;
      if (x - d < 0) now += (x - d) * (x - d - 1) / 2;
    }
    i++;
  }
  cout << i - 2 << endl;
}
