#include <bits/stdc++.h>
#pragma comment(linker, "/STACK:256000000")
using namespace std;
long long n, x, y, c;
long long progr(long long first, long long last, long long cnt) {
  long long ans = first + last;
  if (ans % 2 == 0)
    ans /= 2;
  else {
    assert(cnt % 2 == 0);
    cnt /= 2;
  }
  return ans * cnt;
}
long long vuxid1(long long len) {
  if (len <= 0) return 0;
  return progr(1, 1 + 2 * (len - 1), len);
}
long long vuxid2(long long len) {
  if (len <= 0) return 0;
  return progr(1, 1 + 1 * (len - 1), len);
}
long long check(long long mid) {
  long long ans = 1 + progr(0, 4 * mid, mid + 1);
  long long a[4];
  a[0] = x - 1;
  a[1] = n - y;
  a[2] = n - x;
  a[3] = y - 1;
  for (int i = 0; i < 4; ++i) {
    long long tmp = mid - a[i];
    long long pans = vuxid1(mid - a[i]);
    ans -= vuxid1(mid - a[i]);
  }
  for (int i = 0; i < 4; ++i) {
    long long tmp = mid - a[i] - a[(i + 1) % 4] - 1;
    long long pans = vuxid2(mid - a[i] - a[(i + 1) % 4] - 1);
    ans += vuxid2(mid - a[i] - a[(i + 1) % 4] - 1);
  }
  return ans;
}
int main() {
  cin >> n >> x >> y >> c;
  long long l = -1;
  long long r = 2 * n + 1;
  check(11);
  while (l < r - 1) {
    long long mid = (l + r) / 2;
    if (check(mid) >= c)
      r = mid;
    else
      l = mid;
  }
  cout << r << endl;
  return 0;
}
