source_code: import java.io.*;
  import java.util.*;
  
  public class Example {
  
      BufferedReader in;
      PrintWriter out;
      StringTokenizer st;
  
      String next() {
          while (st == null || !st.hasMoreTokens()) {
              try {
                  st = new StringTokenizer(in.readLine());
              } catch (Exception e) {
              }
          }
          return st.nextToken();
      }
  
      int nextInt() {
          return Integer.parseInt(next());
      }
  
      long nextLong() {
          return Long.parseLong(next());
      }
  
      double nextDouble() {
          return Double.parseDouble(next());
      }
  
      public void run() throws Exception {
          //in = new BufferedReader(new FileReader("input.txt"));
          //out = new PrintWriter(new FileWriter("output.txt"));
          in = new BufferedReader(new InputStreamReader(System.in));
          out = new PrintWriter(System.out);
          solve();
          out.flush();
          out.close();
          in.close();
      }
      long n, x, y, c;
  
      boolean check(long z) {
          long res = 1 + 2 * z * (z + 1);
          long bx1 = z - x + 1;
          long by1 = z - y + 1;
          long bxn = z - n + x;
          long byn = z - n + y;
  
          if (bx1 > 0) {
              res -= bx1 * bx1;
          }
          if (bxn > 0) {
              res -= bxn * bxn;
          }
          if (by1 > 0) {
              res -= by1 * by1;
          }
          if (byn > 0) {
              res -= byn * byn;
          }
  
          if (z > x + y - 1) {
              long m = z - x - y + 1;
              res += m * (m + 1) / 2;
          }
          if (z > x + n - y) {
              long m = z - x - n + y;
              res += m * (m + 1) / 2;
          }
          if (z > n - x + y) {
              long m = z - n - y + x;
              res += m * (m + 1) / 2;
          }
          if (z > n - x + n - y + 1) {
              long m = z - 2 * n + x + y - 1;
              res += m * (m + 1) / 2;
          }
          
          return res >= c;
      }
  
      public void solve() throws Exception {
          n = nextLong();
          x = nextLong();
          y = nextLong();
          c = nextLong();
          long l = 0;
          long r = 2 * n;
          while (r > l) {
              long mid = (r + l) / 2;
              if (check(mid)) {
                  r = mid;
              } else {
                  l = mid + 1;
              }
          }
          out.println(r);
      }
  
      public static void main(String[] args) throws Exception {
          new Example().run();
      }
  }