#include <bits/stdc++.h>
using namespace std;
long long countafter(int x, int y, int t, int n) {
  t--;
  int lowest = max(x - t, 1);
  int highest = min(x + t, n);
  long long answer = 0;
  for (int xp = lowest; xp <= highest; xp++) {
    int miny = max(1, y - t + abs(x - xp));
    int maxy = min(n, y + t - abs(x - xp));
    if (miny > maxy) continue;
    answer += maxy - miny + 1;
  }
  return answer;
}
int main() {
  int n, x, y, c;
  cin >> n >> x >> y >> c;
  if (c == 1) {
    cout << 0 << endl;
    return 0;
  }
  long long low = 0;
  long long high = 1000000;
  while (low < high) {
    long long mid = (low + high) / 2;
    if (countafter(x, y, mid, n) >= c) {
      high = mid;
    } else {
      low = mid + 1;
    }
  }
  cout << low - 1 << endl;
}
