#include <bits/stdc++.h>
using namespace std;
long long n, x, y;
long long c;
long long compute(long long x, long long y, long long mid) {
  long long L = mid;
  if ((n - x) + (n - y) <= L) return (((long long)n - x + 1) * (n - y + 1));
  long long ret = (L + 2) * (L + 1) / 2;
  if (x + mid >= n)
    ret -= ((long long)x + mid - n) * ((long long)x + mid - n + 1) / 2;
  if (y + mid >= n)
    ret -= ((long long)y + mid - n) * ((long long)y + mid - n + 1) / 2;
  return ret;
}
long long check(long long mid) {
  if (mid == 0) return 1;
  long long ret = compute(x, y, mid) + compute(n - x + 1, y, mid) +
                  compute(x, n - y + 1, mid) +
                  compute(n + 1 - x, n + 1 - y, mid);
  ret -= min(n, x + mid) - max(1ll, x - mid) + 1;
  ret -= min(n, y + mid) - max(1ll, y - mid) + 1;
  ret -= 1;
  return ret;
}
int main() {
  cin >> n >> x >> y >> c;
  long long g = 0, h = 2 * n, ans = 0;
  while (g <= h) {
    int mid = (g + h) / 2;
    if (check(mid) >= c)
      ans = mid, h = mid - 1;
    else
      g = mid + 1;
  }
  cout << ans << endl;
  return 0;
}
