#include <bits/stdc++.h>
using namespace std;
bool flag(long long n, long long x, long long y, long long c, long long t) {
  long long square = 0, s = t, k;
  square += s * s;
  square += (s + 1) * (s + 1);
  if (x <= t) {
    k = t - x + 1;
    square -= k * k;
  }
  if (x > n - t) {
    k = x + t - n;
    square -= k * k;
  }
  if (y <= t) {
    k = t - y + 1;
    square -= k * k;
  }
  if (y > n - t) {
    k = y + t - n;
    square -= k * k;
  }
  if (t >= x + y) {
    k = t - x - y + 1;
    square += k * (k + 1) / 2;
  }
  if (t - (n - x + 2 + n - y) >= 0) {
    k = t - (n - x + 2 + n - y) + 1;
    square += k * (k + 1) / 2;
  }
  if (t >= x - y + n + 1) {
    k = t - (x + n + 1 - y) + 1;
    square += k * (k + 1) / 2;
  }
  if (t >= n - x + y + 1) {
    k = t - (n - x + y + 1) + 1;
    square += k * (k + 1) / 2;
  }
  return (square >= c);
}
long long run(long long a, long long b, long long n, long long x, long long y,
              long long c) {
  if (a == b) return a;
  long long m = (a + b) / 2;
  if (flag(n, x, y, c, m))
    return run(a, m, n, x, y, c);
  else
    return run(m + 1, b, n, x, y, c);
}
int main() {
  long long n, x, y, c;
  cin >> n >> x >> y >> c;
  flag(n, x, y, c, 5e8);
  cout << run(0, 1e9, n, x, y, c);
  return 0;
}
