#include <bits/stdc++.h>
#pragma comment(linker, "/STACK:256000000")
using namespace std;
long long sum(int n) { return 1LL * (n) * (n + 1) / 2; }
long long get(int x, int y, int m) {
  long long ret = 0;
  if (x < 1 || y < 1 || m <= 0) return 0;
  int addx = max(m - x, 0), addy = max(m - y, 0);
  ret += 1LL * (addx) * (addx + 1) / 2 + 1LL * (addy) * (addy + 1) / 2;
  ret -= sum(max(m - x - y, 0));
  return sum(m) - ret;
}
int main() {
  int n, x, y, c;
  cin >> n >> x >> y >> c;
  int l = 0, r = 2 * n + 1;
  while (r - l > 1) {
    int m = (l + r) >> 1;
    long long sum = get(x, y, m);
    sum += get(x, n - y, m - 1);
    sum += get(n - x, y, m - 1);
    sum += get(n - x, n - y, m - 2);
    if (sum >= c)
      r = m;
    else
      l = m;
  }
  cout << r - 1 << endl;
  return 0;
}
