#include <bits/stdc++.h>
using namespace std;
int main() {
  long long x, y, n, c;
  scanf("%I64d %I64d %I64d %I64d", &n, &x, &y, &c);
  long long hi = c / 2, low = 0, mid = (hi + low) / 2;
  int l = 0, r = 0, t = 0, b = 0;
  float s = 1.0;
  while (mid < hi) {
    s = mid * mid * 2 + mid * 2 + 1;
    l = x + mid - n, r = y + mid - n, t = mid - x + 1, b = mid - y + 1;
    if (x + mid > n) {
      s -= l * l;
    }
    if (y + mid > n) {
      s -= r * r;
    }
    if (mid - x > -1) {
      s -= t * t;
    }
    if (mid - y > -1) {
      s -= b * b;
    }
    l = mid - x - y + 1, r = mid - n + x - y, t = mid - n + y - x,
    b = mid - 2 * n + x + y - 1;
    if (l > 0) {
      s += 0.5 * l * l + 0.5 * l;
    }
    if (r > 0) {
      s += 0.5 * r * r + 0.5 * r;
    }
    if (t > 0) {
      s += 0.5 * t * t + 0.5 * t;
    }
    if (b > 0) {
      s += 0.5 * b * b + 0.5 * b;
    }
    if (s >= c)
      hi = mid;
    else
      low = mid + 1;
    mid = (hi + low) / 2;
  }
  printf("%I64d", mid);
}
