#include <bits/stdc++.h>
using namespace std;
long long sum, mid, n, x, y, c, l, r, ans;
long long go(long long mid) {
  sum = 0;
  sum += mid * mid + (mid - 1) * (mid - 1);
  if (mid > x) sum -= (mid - x) * (mid - x);
  if (mid > y) sum -= (mid - y) * (mid - y);
  if (mid > (n - x) + 1) sum -= (mid - (n - x) - 1) * (mid - (n - x) - 1);
  if (mid > (n - y) + 1) sum -= (mid - (n - y) - 1) * (mid - (n - y) - 1);
  if (mid > x + y) sum += (mid - x - y) * (mid - x - y + 1) / 2;
  if (mid > y + n - x + 1)
    sum += (mid - y - (n - x) - 1) * (mid - y - (n - x)) / 2;
  if (mid > x + (n - y) + 1)
    sum += (mid - x - (n - y) - 1) * (mid - x - (n - y)) / 2;
  if (mid > (n - x) + (n - y) + 2)
    sum += (mid - (n - x) - (n - y) - 2) * (mid - (n - x) - (n - y) - 1) / 2;
  if (sum >= c) return 1;
  return 0;
}
int main() {
  cin >> n >> x >> y >> c;
  if (c == 1) {
    cout << 0;
    return 0;
  }
  l = 0;
  r = 2000000000;
  while (l <= r) {
    mid = (l + r) / 2;
    if (go(mid)) {
      ans = mid;
      r = mid - 1;
    } else
      l = mid + 1;
  }
  cout << ans - 1;
}
