Mr. Bender has a digital table of size n × n, each cell can be switched on or off. He wants the field to have at least c switched on squares. When this condition is fulfilled, Mr Bender will be happy.

We'll consider the table rows numbered from top to bottom from 1 to n, and the columns — numbered from left to right from 1 to n. Initially there is exactly one switched on cell with coordinates (x, y) (x is the row number, y is the column number), and all other cells are switched off. Then each second we switch on the cells that are off but have the side-adjacent cells that are on.

For a cell with coordinates (x, y) the side-adjacent cells are cells with coordinates (x - 1, y), (x + 1, y), (x, y - 1), (x, y + 1).

In how many seconds will Mr. Bender get happy?

Input

The first line contains four space-separated integers n, x, y, c (1 ≤ n, c ≤ 109; 1 ≤ x, y ≤ n; c ≤ n2).

Output

In a single line print a single integer — the answer to the problem.

Examples

Input

6 4 3 1


Output

0


Input

9 3 8 10


Output

2

Note

Initially the first test has one painted cell, so the answer is 0. In the second test all events will go as is shown on the figure. <image>.
import java.io.*;
import java.util.*;
//I am fading.......
//read the question correctly (is y a vowel? what are the exact constraints?)
//look out for SPECIAL CASES (n=1?) and overflow (ll vs int?)
public class Main
{
	static long lul(long hol)
	{
		if(hol<0) return 0;
		return (hol*(hol-1))/2;
	}
	static long hola(long lol)
	{
		if(lol<0) return 0;
		return lol*lol;
	}
	public static void main(String[] args) throws Exception
	{
		long n=ni(),x=ni(),y=ni(),c=ni();
		long low=0,high=2*n,mid=(low+high)/2;
		while(low<high)
		{
			long cur=2*(mid+1)*(mid+1)-2*(mid+1)+1;
			cur-=hola(mid-(x-1))+hola(mid-(n-x))+hola(mid-(y-1))+hola(mid-(n-y));
			cur+=lul(mid-(x-1+y-1))+lul(mid-(n-x+y-1))+lul(mid-(n-x+n-y))+lul(mid-(n-y+x-1));
			if(cur<c)
				low=mid+1;
			else
				high=mid;
			mid=(low+high)/2;
		}
		sop(mid);
		System.out.print(output);
	}
	
	///////////////////////////////////////////
	///////////////////////////////////////////
	///template from here
	
	static class pair
	{
		int a,b;
		boolean boolran;
		pair(){}
		pair(int c,int d){a=c;b=d;}
		@Override
		public int hashCode(){return (a+" "+b).hashCode();}
		@Override public boolean equals(Object c){if(a==((pair)c).a&&b==((pair)c).b)return true;return false;}
	}
	static interface combiner
	{
		public int combine(int a, int b);
	}
	static final int mod=1000000007;
	static final double eps=1e-9;
	static final long inf=100000000000000000L;
	static Reader in=new Reader();
	static StringBuilder output=new StringBuilder();
	static Random rn=new Random();
	static void reverse(int[]a){for(int i=0; i<a.length/2; i++){a[i]^=a[a.length-i-1];a[a.length-i-1]^=a[i];a[i]^=a[a.length-i-1];}}
	static void sort(int[]a)
	{
		int te;
		for(int i=0; i<a.length; i+=2)
		{
			te=rn.nextInt(a.length);
			if(i!=te)
			{
				a[i]^=a[te];
				a[te]^=a[i];
				a[i]^=a[te];
			}
		}
		Arrays.sort(a);
	}
	static void sort(long[]a)
	{
		int te;
		for(int i=0; i<a.length; i+=2)
		{
			te=rn.nextInt(a.length);
			if(i!=te)
			{
			a[i]^=a[te];
			a[te]^=a[i];
			a[i]^=a[te];
			}
		}
		Arrays.sort(a);
	}
	static void sort(double[]a)
	{
		int te;
		double te1;
		for(int i=0; i<a.length; i+=2)
		{
			te=rn.nextInt(a.length);
			if(i!=te)
			{
			te1=a[te];
			a[te]=a[i];
			a[i]=te1;
			}
		}
		Arrays.sort(a);
	}
	static void sort(int[][]a)
	{
		Arrays.sort(a, new Comparator<int[]>()
		{
			public int compare(int[]a,int[]b)
			{
				if(a[0]>b[0])
					return -1;
				if(b[0]>a[0])
					return 1;
				return 0;
			}
		});
	}
	static void sort(pair[]a)
	{
		Arrays.sort(a,new Comparator<pair>()
				{
			@Override
			public int compare(pair a,pair b)
			{
				if(a.a>b.a)
					return 1;
				if(b.a>a.a)
				return -1;
				return 0;
			}
				});
	}
	static int log2n(long a)
	{
		int te=0;
		while(a>0)
		{
			a>>=1;
			++te;
		}
		return te;
	}
	static class vecti
	{
		int a[],size;
		vecti(){a=new int[10];size=0;}
		vecti(int n){a=new int[n];size=0;}
		public void add(int b){if(++size==a.length)a=Arrays.copyOf(a, 2*size);a[size-1]=b;}
		public void sort(){Arrays.sort(a, 0, size);}
		public void sort(int l, int r){Arrays.sort(a, l, r);}
	}
	//output functions////////////////
	static void pr(Object a){output.append(a+"\n");}
	static void pr(){output.append("\n");}
	static void p(Object a){output.append(a);}
	static void pra(int[]a){for(int i:a)output.append(i+" ");output.append("\n");}
	static void pra(long[]a){for(long i:a)output.append(i+" ");output.append("\n");}
	static void pra(String[]a){for(String i:a)output.append(i+" ");output.append("\n");}
	static void pra(double[]a){for(double i:a)output.append(i+" ");output.append("\n");}
	static void sop(Object a){System.out.println(a);}
	static void flush(){System.out.println(output);output=new StringBuilder();}
	//////////////////////////////////
	//input functions/////////////////
	static int ni(){return Integer.parseInt(in.next());}
	static long nl(){return Long.parseLong(in.next());}
	static String ns(){return in.next();}
	static double nd(){return Double.parseDouble(in.next());}
	static int[] nia(int n){int a[]=new int[n];for(int i=0; i<n; i++)a[i]=ni();return a;}
	static int[] pnia(int n){int a[]=new int[n+1];for(int i=1; i<=n; i++)a[i]=ni();return a;}
	static long[] nla(int n){long a[]=new long[n];for(int i=0; i<n; i++)a[i]=nl();return a;}
	static String[] nsa(int n){String a[]=new String[n];for(int i=0; i<n; i++)a[i]=ns();return a;}
	static double[] nda(int n){double a[]=new double[n];for(int i=0; i<n; i++)a[i]=nd();return a;}
	//////////////////////////////////
	//some utility functions
	static void exit(){System.out.print(output);System.exit(0);}
	static int min(int... a){int min=a[0];for(int i:a)min=Math.min(min, i);return min;}
	static int max(int... a){int max=a[0];for(int i:a)max=Math.max(max, i);return max;}	
	static int gcd(int... a){int gcd=a[0];for(int i:a)gcd=gcd(gcd, i);return gcd;}	
	static long min(long... a){long min=a[0];for(long i:a)min=Math.min(min, i);return min;}
	static long max(long... a){long max=a[0];for(long i:a)max=Math.max(max, i);return max;}	
	static long gcd(long... a){long gcd=a[0];for(long i:a)gcd=gcd(gcd, i);return gcd;}	
	static String pr(String a, long b){String c="";while(b>0){if(b%2==1)c=c.concat(a);a=a.concat(a);b>>=1;}return c;}
	static long powm(long a, long b, long m){long an=1;long c=a;while(b>0){if(b%2==1)an=(an*c)%m;c=(c*c)%m;b>>=1;}return an;}
	static int gcd(int a, int b){if(b==0)return a;return gcd(b, a%b);}
	static long gcd(long a, long b){if(b==0)return a;return gcd(b, a%b);}
	static class Reader {
        public BufferedReader reader;
        public StringTokenizer tokenizer;
        public Reader() {
            reader = new BufferedReader(new InputStreamReader(System.in), 32768);
            tokenizer = null;
        }
        public String next() {
            while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        }
    }
}