#include <bits/stdc++.h>
using namespace std;
long long n, sx, sy, c;
long long ans;
long long calc(long long s, long long t, long long d) {
  return s <= t ? (s + t) * ((t - s) / d + 1) / 2 : 0;
}
bool legal(long long m) {
  long long res = 0;
  res = calc(1, 2 * m - 1, 2) * 2 + 2 * m + 1;
  long long lef = sy - m, up = sx - m, rig = sy + m, dow = sx + m;
  res -= calc(1, 2 * (1 - lef) - 1, 2) + calc(1, 2 * (1 - up) - 1, 2) +
         calc(1, 2 * (rig - n) - 1, 2) + calc(1, 2 * (dow - n) - 1, 2);
  long long dl = sy, du = sx, dr = n - sy + 1, dd = n - sx + 1;
  res += calc(1, 1 - lef - du, 1) + calc(1, 1 - up - dr, 1) +
         calc(1, rig - n - dd, 1) + calc(1, dow - n - dl, 1);
  return res >= c;
}
signed main() {
  cin >> n >> sx >> sy >> c;
  long long l = 0, r = 2 * n;
  while (l <= r) {
    long long mid = l + r >> 1;
    if (legal(mid)) {
      ans = mid;
      r = mid - 1;
    } else
      l = mid + 1;
  }
  cout << ans << endl;
  return 0;
}
