#include <bits/stdc++.h>
using namespace std;
long long n, x, y, c;
long long sum(long long a1, long long n, long long q) {
  return (a1 + a1 + (n - 1) * q) * n / 2;
}
bool stg(long long k) {
  long long q = sum(0, k + 1, 4) + 1;
  long long rr = x + k;
  if (rr > n) {
    q -= sum(1, (rr - n), 2);
  }
  long long ll = x - k;
  if (ll < 1) {
    q -= sum(1, (1 - ll), 2);
  }
  long long uu = y + k;
  if (uu > n) {
    q -= sum(1, (uu - n), 2);
  }
  long long dd = y - k;
  if (dd < 1) {
    q -= sum(1, (1 - dd), 2);
  }
  if (uu > n) {
    long long e = (1 + (2 * (uu - n - 1)));
    if (x + ((e - 1) / 2) > n) {
      q += sum(1, ((x + ((e - 1) / 2)) - n), 1);
    }
    if (x - ((e - 1) / 2) < 1) {
      q += sum(1, (1 - (x - ((e - 1) / 2))), 1);
    }
  }
  if (dd < 1) {
    long long e = (1 + (2 * (1 - dd - 1)));
    if (x + ((e - 1) / 2) > n) {
      q += sum(1, ((x + ((e - 1) / 2)) - n), 1);
    }
    if (x - ((e - 1) / 2) < 1) {
      q += sum(1, (1 - (x - ((e - 1) / 2))), 1);
    }
  }
  return (q >= c);
}
long long byn() {
  long long l = 0, r = n + n + n;
  while ((r - l) > 3) {
    long long m = (l + r) / 2;
    if (stg(m))
      r = m;
    else
      l = m;
  }
  for (long long m = l; m <= r; ++m) {
    if (stg(m)) return m;
  }
}
int main() {
  cin >> n >> x >> y >> c;
  cout << byn() << endl;
  ;
  return 0;
}
