#include <bits/stdc++.h>
using namespace std;
int n, x, y, c;
bool check(int i, int j) {
  if (i < 1 || j < 1) return false;
  if (i > n || j > n) return false;
  return true;
}
int dx[] = {0, 0, 1, -1};
int dy[] = {1, -1, 0, 0};
int main() {
  scanf("%d", &n);
  scanf("%d", &x);
  scanf("%d", &y);
  scanf("%d", &c);
  int sec = 0, cnt = 1;
  while (cnt < c) {
    sec++;
    int nx, ny, nx2, ny2;
    ny = max(1, y - sec), nx = x + y - sec - ny;
    nx2 = max(1, x - sec), ny2 = x + y - sec - nx2;
    if (ny2 >= ny) cnt += (ny2 - ny + 1);
    ny = min(n, y + sec), nx = x + y + sec - ny;
    nx2 = min(n, x + sec), ny2 = x + y + sec - nx2;
    if (ny >= ny2) cnt += (ny - ny2 + 1);
    ny = max(1, y - sec), nx = x - y + sec + ny;
    nx2 = min(n, x + sec), ny2 = nx2 - (x - y + sec);
    if (ny2 >= ny) cnt += (ny2 - ny + 1);
    ny = min(n, y + sec), nx = x - y - sec + ny;
    nx2 = max(1, x - sec), ny2 = nx2 - (x - y - sec);
    if (ny >= ny2) cnt += (ny - ny2 + 1);
    for (int i = 0; i < 4; i++) {
      nx = x + dx[i] * sec, ny = y + dy[i] * sec;
      cnt -= check(nx, ny);
    }
  }
  cout << sec << endl;
  return 0;
}
