#include <bits/stdc++.h>
const long double PI = 3.141592653589793238L;
const long long N = 300005;
using namespace std;
long long sum(long long a, long long b) {
  return (b >= a) ? (((b - a + 1) * (b + a)) / 2) : 0ll;
}
long long f(long long a, long long x, long long b, long long mn) {
  if (mn >= x) return sum(a, x) + sum(b, x) - x;
  if (mn >= max(a, b))
    return ((2 * (x - mn + 1) - 1) * mn) + sum(a, mn - 1) + sum(b, mn - 1);
  if (mn <= min(a, b)) return ((x - a + 1) + (x - b + 1) - 1) * mn;
  if (mn < b) return sum(a, mn) + f(mn + 1, x, b, mn);
  if (mn < a) return sum(b, mn) + f(a, x, mn + 1, mn);
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  long long n, x, y, c;
  cin >> n >> x >> y >> c;
  long long i = 0, j = 2e18;
  long long ans;
  while (i <= j) {
    long long mid = (i + j) / 2;
    long long left = min(y - 1, mid);
    long long right = min(n - y, mid);
    long long top = f(mid - left, mid, mid - right, x - 1);
    long long down = f(mid - left, mid, mid - right, n - x);
    if (top + down + left + right + 1 >= c)
      ans = mid, j = mid - 1;
    else
      i = mid + 1;
  }
  cout << ans << '\n';
  return 0;
}
