#include <bits/stdc++.h>
using namespace std;
const double pi = acos(-1.0);
long long n, x, y, c;
long long getloc(long long a, long long b, long long d) {
  if (a > b) swap(a, b);
  if (a >= d && b >= d) return d * (d + 1) / 2;
  if (a < d && b >= d) return (d - a) * a + a * (a + 1) / 2;
  if (d >= (a + b - 1)) return a * b;
  d = (a + b - 1 - d);
  return a * b - d * (d + 1) / 2;
}
long long get(long long d) {
  return getloc(x - 1, y - 1, max(0ll, d - 1)) +
         getloc(n - x, n - y, max(0ll, d - 1)) +
         getloc(x - 1, n - y, max(0ll, d - 1)) +
         getloc(n - x, y - 1, max(0ll, d - 1)) + min(x - 1, d) + min(y - 1, d) +
         min(n - x, d) + min(n - y, d) + 1;
}
int main() {
  cin >> n >> x >> y >> c;
  long long lb = 0;
  long long rb = 2 * n;
  while (lb < rb) {
    long long mid = (lb + rb) / 2;
    if (get(mid) < c)
      lb = mid + 1;
    else
      rb = mid;
  }
  cout << lb << endl;
  return 0;
}
