#include <bits/stdc++.h>
using namespace std;
long long x, y, n, c;
long long sum(long long s) { return s * (s + 1) / 2; }
long long min(long long a, long long b) {
  if (a < b)
    return a;
  else
    return b;
}
long long gao(long long k) {
  long long ret = 0;
  if (x - 1 + y - 1 <= k)
    ret = x * y;
  else {
    ret = sum(k + 1);
    if (x <= k) ret -= sum(k - x + 1);
    if (y <= k) ret -= sum(k - y + 1);
  }
  if (x - 1 + n - y <= k)
    ret += x * (n - y + 1);
  else {
    ret += sum(k + 1);
    if (x <= k) ret -= sum(k - x + 1);
    if (y + k > n) ret -= sum(y + k - n);
  }
  if (n - x + y - 1 <= k)
    ret += (n - x + 1) * y;
  else {
    ret += sum(k + 1);
    if (x + k > n) ret -= sum(x + k - n);
    if (y <= k) ret -= sum(k - y + 1);
  }
  if (n - x + n - y <= k)
    ret += (n - x + 1) * (n - y + 1);
  else {
    ret += sum(k + 1);
    if (x + k > n) ret -= sum(x + k - n);
    if (y + k > n) ret -= sum(y + k - n);
  }
  ret -= min(k + 1, x);
  ret -= min(k + 1, y);
  ret -= min(k + 1, n - y + 1);
  ret -= min(k + 1, n - x + 1);
  return ret + 1;
}
int main() {
  cin >> n >> x >> y >> c;
  long long lefts = 0;
  long long rights = 10 * n;
  long long ans = 0;
  while (lefts <= rights) {
    long long mid = (lefts + rights) / 2;
    if (gao(mid) >= c) {
      ans = mid;
      rights = mid - 1;
    } else
      lefts = mid + 1;
  }
  cout << ans << endl;
  return 0;
}
