#include <bits/stdc++.h>
using namespace std;
int n, m, x, y, z, w;
int high, low, mid;
long long k, tmp;
long long solve(int x, int y, int t) {
  int incto = min(x, y);
  int startdec = max(x, y);
  int end = startdec + incto;
  if (t <= incto) {
    long long a = t;
    return (a + 1ll) * (a + 2ll) / 2ll;
  } else if (t > incto && t <= startdec) {
    long long a = incto;
    a = (a + 1ll) * (a + 2ll) / 2ll;
    a += (long long)(t - incto) * (long long)(incto + 1);
    return a;
  } else if (t > startdec && t <= end) {
    long long a = incto;
    long long b = incto;
    a = (a + 1ll) * (a + 2ll) / 2ll;
    a += (long long)(startdec - incto) * (long long)(incto + 1);
    a += b * (b + 1ll) / 2ll;
    long long c = end - t;
    a -= c * (c + 1ll) / 2ll;
    return a;
  } else if (t > end) {
    long long a = incto;
    long long b = incto;
    a = (a + 1ll) * (a + 2ll) / 2ll;
    a += (long long)(startdec - incto) * (long long)(incto + 1);
    a += b * (b + 1ll) / 2ll;
    return a;
  }
}
int main() {
  scanf("%d %d %d %I64d", &n, &x, &y, &k);
  if (k <= 1ll) {
    printf("0\n");
    return 0;
  }
  x--;
  y--;
  high = n * 2;
  low = 0;
  while (high - low > 1) {
    mid = (high + low) / 2;
    tmp = solve(x, y, mid);
    tmp += solve(x, n - y - 1, mid);
    tmp += solve(n - x - 1, y, mid);
    tmp += solve(n - x - 1, n - y - 1, mid);
    tmp -= (long long)min(x, mid);
    tmp -= (long long)min(y, mid);
    tmp -= (long long)min(n - x - 1, mid);
    tmp -= (long long)min(n - y - 1, mid);
    tmp -= 3ll;
    if (tmp >= k)
      high = mid;
    else
      low = mid;
  }
  printf("%d\n", high);
  return 0;
}
