#include <bits/stdc++.h>
using namespace std;
const int INF = 0x3f3f3f3f;
const long long LLINF = 1e18;
const int maxN = 1e5;
long long n, row, col, c;
long long sum(long long t) {
  long long max_l = col - 1, max_r = n - col;
  long long ans = 0;
  ans += 1 + min(t, max_l) + min(t, max_r);
  long long aux_t = t;
  for (int i = row - 1; i >= 1; i--) {
    aux_t--;
    if (aux_t < 0) break;
    ans += 1 + min(aux_t, max_l) + min(aux_t, max_r);
  }
  for (int i = row + 1; i <= n; i++) {
    t--;
    if (t < 0) break;
    ans += 1 + min(t, max_l) + min(t, max_r);
  }
  return ans;
}
int main() {
  scanf("%lld %lld", &n, &row), scanf("%lld %lld", &col, &c);
  long long lo = 0, hi = 1e6;
  while (lo < hi) {
    long long mi = lo + (hi - lo) / 2;
    if (sum(mi) >= c)
      hi = mi;
    else
      lo = mi + 1;
  }
  printf("%lld\n", hi);
  return 0;
}
