#include <bits/stdc++.h>
using namespace std;
template <typename T>
T sqr(T x) {
  return x * x;
}
template <typename T>
T Abs(T x) {
  return x > 0 ? x : -x;
}
long long c, n, x, y, l, r, mid, ans;
int main() {
  cin >> n >> x >> y >> c;
  l = 0;
  r = n + n - 2;
  while (l <= r) {
    mid = (l + r) / 2;
    long long tot = 0;
    if (x - mid <= 0) tot += sqr(Abs(x - mid - 1));
    if (x - mid <= 0 && y - mid <= 0) {
      long long res = mid - (x - 1) - (y - 1) - 1;
      if (res > 0) tot -= (sqr(res) + res) / 2;
    }
    if (x + mid > n) tot += sqr(x + mid - n);
    if (x - mid <= 0 && y + mid > n) {
      long long res = mid - (x - 1) - (n - y) - 1;
      if (res > 0) tot -= (sqr(res) + res) / 2;
    }
    if (y - mid <= 0) tot += sqr(Abs(y - mid - 1));
    if (x + mid > n && y - mid <= 0) {
      long long res = mid - (n - x) - (y - 1) - 1;
      if (res > 0) tot -= (sqr(res) + res) / 2;
    }
    if (y + mid > n) tot += sqr(y + mid - n);
    if (x + mid > n && y + mid > n) {
      long long res = mid - (n - x) - (n - y) - 1;
      if (res > 0) tot -= (sqr(res) + res) / 2;
    }
    tot = sqr(mid) + sqr(mid + 1) - tot;
    if (tot >= c)
      ans = mid, r = mid - 1;
    else
      l = mid + 1;
  }
  cout << ans << endl;
  return 0;
}
