#include <bits/stdc++.h>
using namespace std;
long long l, r, u, d;
long long n, x, y, c;
long long sqr(long long x) { return x * x; }
long long tri(long long x) { return (x + 1) * x / 2; }
bool solve(long long t) {
  long long sum = t * t + (t + 1) * (t + 1);
  if (t > l) sum -= sqr(t - l);
  if (t > r) sum -= sqr(t - r);
  if (t > u) sum -= sqr(t - u);
  if (t > d) sum -= sqr(t - d);
  if (t > l + d) sum += tri(t - (l + d) - 1);
  if (t > l + u) sum += tri(t - (l + u) - 1);
  if (t > r + d) sum += tri(t - (r + d) - 1);
  if (t > r + u) sum += tri(t - (r + u) - 1);
  if (sum >= c) return true;
  return false;
}
int main() {
  while (~scanf("%I64d%I64d%I64d%I64d", &n, &x, &y, &c)) {
    l = x - 1, r = n - x;
    u = y - 1, d = n - y;
    long long low = 0, high = 2 * n, mid;
    while (low <= high) {
      mid = (low + high) / 2;
      if (solve(mid))
        high = mid - 1;
      else
        low = mid + 1;
    }
    printf("%I64d\n", low);
  }
  return 0;
}
