#include <bits/stdc++.h>
using namespace std;
const long long M = 2e5 + 5;
const long long INF = 1e15 + 5;
const long long MOD = 1e9 + 7;
const long long N = 1e5 + 5;
const double PI = 3.14159265358979323846264338327950288419716939937510;
long long n, x, y, c;
long long gi(long long g) {
  if (g <= 0) return 0;
  return g * g;
}
long long gj(long long g) {
  if (g <= 0) return 0;
  return (g * g - g) / 2 + g;
}
long long gett(long long t) {
  long long ss = (2 * t + 1) * (t * 2 + 1);
  ss = ss / 2 + 1;
  ss -= gi(t - (x - 1));
  ss -= gi(t - (n - x));
  ss -= gi(t - (y - 1));
  ss -= gi(t - (n - y));
  ss += gj(t - (x - 1) - (y - 1) - 1);
  ss += gj(t - (n - x) - (n - y) - 1);
  ss += gj(t - (n - x) - (y - 1) - 1);
  ss += gj(t - (x - 1) - (n - y) - 1);
  return ss;
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  cin >> n >> x >> y >> c;
  long long low = 0, high = 2e9;
  while (low < high) {
    long long mid = low + (high - low) / 2;
    if (gett(mid) >= c)
      high = mid;
    else
      low = mid + 1;
  }
  cout << low << "\n";
}
