#include <bits/stdc++.h>
using namespace std;
int n;
int dir[4][2] = {{-1, 0}, {0, 1}, {1, 0}, {0, -1}};
bool out(pair<int, int> p) {
  return p.first > n || p.first < 1 || p.second > n || p.second < 1;
}
void apply(int i, pair<int, int> &p) {
  p.first += dir[i][0];
  p.second += dir[i][1];
}
int main() {
  int X, Y, c, t = 0;
  cin >> n >> X >> Y >> c;
  long long sum = 1, res[4] = {1, 1, 1, 1};
  pair<pair<int, int>, pair<int, int> > dia[4];
  for (int i = 0; i < 4; ++i) {
    pair<int, int> tmp(X + dir[i][0], Y + dir[i][1]);
    dia[i] = pair<pair<int, int>, pair<int, int> >(tmp, tmp);
    if (out(tmp)) res[i] = 0;
  }
  while (sum < c) {
    for (int i = 0; i < 4; ++i) {
      if (res[i] <= 0) continue;
      sum += res[i];
      res[i]++;
      apply(i, dia[i].first);
      apply((i + 1) % 4, dia[i].second);
      if (out(dia[i].first)) {
        apply((i + 1) % 4, dia[i].first);
        apply((i + 2) % 4, dia[i].first);
        res[i]--;
      }
      if (out(dia[i].second)) {
        apply((i + 1) % 4, dia[i].second);
        apply((i + 2) % 4, dia[i].second);
        res[i]--;
      }
    }
    ++t;
  }
  cout << t << endl;
  return 0;
}
