#include <bits/stdc++.h>
using namespace std;
long long n, x, y, c;
long long s1(long long n) {
  if (n <= 0) return 0;
  return n * n;
}
long long s2(long long n) {
  if (n <= 0) return 0;
  return n * (n + 1) / 2;
}
long long check(long long m) {
  long long ret = 0;
  ret += s1(m) + s1(m + 1);
  ret -= s1(m + x - n) + s1(m + y - n) + s1(m - x + 1) + s1(m - y + 1);
  ret += s2(m - (n - x + n - y) - 1);
  ret += s2(m - (n - x + y - 1) - 1);
  ret += s2(m - (x - 1 + n - y) - 1);
  ret += s2(m - (x - 1 + y - 1) - 1);
  return ret;
}
long long binary() {
  long long s = 0, e = n * 2;
  while (s != e) {
    long long m = (s + e) / 2;
    if (check(m) >= c)
      e = m;
    else
      s = m + 1;
  }
  return e;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin >> n >> x >> y >> c;
  cout << binary() << endl;
  return 0;
}
