#include <bits/stdc++.h>
using namespace std;
long long n, x, y, c;
bool ch(long long m) {
  if (m == 0) return c == 1;
  double all = 1 + (m * (m + 1) / 2) * 4;
  double add = m - x + 1;
  if (add > 0) {
    add--;
    all -= (add * (add + 1) / 2) * 2 + add + 1;
  }
  add = m - y + 1;
  if (add > 0) {
    add--;
    all -= (add * (add + 1) / 2) * 2 + add + 1;
  }
  add = m - (n - y + 1) + 1;
  if (add > 0) {
    add--;
    all -= (add * (add + 1) / 2) * 2 + add + 1;
  }
  add = m - (n - x + 1) + 1;
  if (add > 0) {
    add--;
    all -= (add * (add + 1) / 2) * 2 + add + 1;
  }
  long long dx, dy;
  dx = abs(x - 1);
  dy = abs(y - 1);
  add = m - (dx + dy) - 1;
  if (add > 0) {
    all += add * (add + 1) / 2;
  }
  dx = abs(x - 1);
  dy = abs(n - y);
  add = m - (dx + dy) - 1;
  if (add > 0) {
    all += add * (add + 1) / 2;
  }
  dx = abs(n - x);
  dy = abs(y - 1);
  add = m - (dx + dy) - 1;
  if (add > 0) {
    all += add * (add + 1) / 2;
  }
  dx = abs(n - x);
  dy = abs(n - y);
  add = m - (dx + dy) - 1;
  if (add > 0) {
    all += add * (add + 1) / 2;
  }
  return all >= c;
}
int main() {
  ios::sync_with_stdio(0);
  cin >> n >> x >> y >> c;
  long long l = 0, h = 2e9, res = 0;
  while (l <= h) {
    long long m = (l + h) / 2;
    if (ch(m)) {
      res = m;
      h = m - 1;
    } else
      l = m + 1;
  }
  cout << res << endl;
  return 0;
}
