#include <bits/stdc++.h>
using namespace std;
int main() {
  int i, j, n, x, y, m;
  long long k;
  scanf("%d%d%d%lld", &n, &x, &y, &k);
  int l = 0, r = 2 * n, mid;
  long long ans;
  while (l <= r) {
    mid = (l + r) >> 1;
    ans = (long long)mid * mid * 2 + 2 * mid + 1;
    if (x + mid - n >= 0) {
      ans -= (long long)(x + mid - n) * (x + mid - n);
    }
    if (x - mid <= 0) {
      ans -= (long long)(mid - x + 1) * (mid - x + 1);
    }
    if (y + mid - n >= 0) {
      ans -= (long long)(y + mid - n) * (y + mid - n);
    }
    if (y - mid <= 0) {
      ans -= (long long)(mid - y + 1) * (mid - y + 1);
    }
    if (mid >= x + y) {
      ans += (long long)(mid - x - y + 1) * (mid - x - y + 2) / 2;
    }
    if (mid >= n - y + x + 1) {
      ans += (long long)(mid - x - n + y) * (mid - x - n + y + 1) / 2;
    }
    if (mid >= n + y - x + 1) {
      ans += (long long)(mid - y - n + x) * (mid - y - n + x + 1) / 2;
    }
    if (mid >= n - x + n - y + 2) {
      ans += (long long)(mid - n + x - n + y - 1) * (mid - n + x - n + y) / 2;
    }
    if (ans >= k) {
      r = mid - 1;
    } else {
      l = mid + 1;
    }
  }
  printf("%d", r + 1);
  return 0;
}
