#include <bits/stdc++.h>
using namespace std;
long long n, x, y, c;
int main() {
  scanf("%I64d%I64d%I64d%I64d", &n, &x, &y, &c);
  x--;
  y--;
  long long k = 1, sec = 0;
  ;
  long long e_up = y, e_down = y, e_left = x, e_right = x;
  while (k < c) {
    sec++;
    k = ((long long)2 * sec + 1) * ((long long)2 * sec + 1) -
        (long long)2 * sec - 2 * sec * sec;
    e_up--;
    e_down++;
    e_left--;
    e_right++;
    if (sec == 6) {
      x = x + 1;
      x = x - 1;
    }
    if (e_up < 0) {
      long long d = -e_up;
      k -= (2 + (d - 1) * 2) / 2 * d;
    }
    if (e_left < 0) {
      long long d = -e_left;
      k -= (2 + (d - 1) * 2) / 2 * d;
    }
    if (e_down >= n) {
      long long d = e_down - n + 1;
      k -= (2 + (d - 1) * 2) / 2 * d;
    }
    if (e_right >= n) {
      long long d = e_right - n + 1;
      k -= (2 + (d - 1) * 2) / 2 * d;
    }
    if (x + 1 + y + 1 <= sec) {
      long long d = sec + 1 - (x + 1 + y + 1);
      k += (long long)(1 + d) * d / 2;
    }
    if (n - x + n - y <= sec) {
      long long d = sec + 1 - (n - x + n - y);
      k += (long long)(1 + d) * d / 2;
    }
    if (n - x + 1 + y <= sec) {
      long long d = sec + 1 - (n - x + y + 1);
      k += (long long)(1 + d) * d / 2;
    }
    if (x + 1 + n - y <= sec) {
      long long d = sec + 1 - (x + 1 + n - y);
      k += (long long)(1 + d) * d / 2;
    }
  }
  printf("%I64d", sec);
  return 0;
}
