Problem: You are given two integers n and k. Find k-th smallest divisor of n, or report that it doesn't exist.

Divisor of n is any such natural number, that n can be divided by it without remainder.

Input

The first line contains two integers n and k (1 ≤ n ≤ 1015, 1 ≤ k ≤ 109).

Output

If n has less than k divisors, output -1.

Otherwise, output the k-th smallest divisor of n.

Examples

Input

4 2


Output

2


Input

5 3


Output

-1


Input

12 5


Output

6

Note

In the first example, number 4 has three divisors: 1, 2 and 4. The second one is 2.

In the second example, number 5 has only two divisors: 1 and 5. The third divisor doesn't exist, so the answer is -1.

Solution (in JAVA):

Solution:


import java.util.*;
import static java.lang.System.out;

import java.io.DataInputStream; 
import java.io.FileInputStream; 
import java.io.IOException; 
import java.io.InputStreamReader;
import java.math.BigInteger; 

public class Main 
{ 

	static int mod = 1000000007;
	static int MOD = 1000000007;
	static final long M = (int)1e9+7;
	 
	
	static class Reader 
	{ 
		final private int BUFFER_SIZE = 1 << 16; 
		private DataInputStream din; 
		private byte[] buffer; 
		private int bufferPointer, bytesRead; 

		public Reader() 
		{ 
			din = new DataInputStream(System.in); 
			buffer = new byte[BUFFER_SIZE]; 
			bufferPointer = bytesRead = 0; 
		} 

		public Reader(String file_name) throws IOException 
		{ 
			din = new DataInputStream(new FileInputStream(file_name)); 
			buffer = new byte[BUFFER_SIZE]; 
			bufferPointer = bytesRead = 0; 
		} 

		public String next() throws IOException 
		{ 
			byte[] buf = new byte[64]; // line length 
			int cnt = 0, c; 
			while ((c = read()) != -1) 
			{ 
				if (c == '\n') 
					break; 
				buf[cnt++] = (byte) c; 
			} 
			return new String(buf, 0, cnt); 
		} 
		
		public int nextInt() throws IOException 
		{ 
			int ret = 0; 
			byte c = read(); 
			while (c <= ' ') 
				c = read(); 
			boolean neg = (c == '-'); 
			if (neg) 
				c = read(); 
			do
			{ 
				ret = ret * 10 + c - '0'; 
			} while ((c = read()) >= '0' && c <= '9'); 

			if (neg) 
				return -ret; 
			return ret; 
		}
		int[] readArray(int n) throws IOException {
			int[] a=new int[n];
			for (int i=0; i<n; i++) a[i]=nextInt();
			return a;
		}

		public long nextLong() throws IOException 
		{ 
			long ret = 0; 
			byte c = read(); 
			while (c <= ' ') 
				c = read(); 
			boolean neg = (c == '-'); 
			if (neg) 
				c = read(); 
			do { 
				ret = ret * 10 + c - '0'; 
			} 
			while ((c = read()) >= '0' && c <= '9'); 
			if (neg) 
				return -ret; 
			return ret; 
		} 

		public double nextDouble() throws IOException 
		{ 
			double ret = 0, div = 1; 
			byte c = read(); 
			while (c <= ' ') 
				c = read(); 
			boolean neg = (c == '-'); 
			if (neg) 
				c = read(); 

			do { 
				ret = ret * 10 + c - '0'; 
			} 
			while ((c = read()) >= '0' && c <= '9'); 

			if (c == '.') 
			{ 
				while ((c = read()) >= '0' && c <= '9') 
				{ 
					ret += (c - '0') / (div *= 10); 
				} 
			} 

			if (neg) 
				return -ret; 
			return ret; 
		} 

		private void fillBuffer() throws IOException 
		{ 
			bytesRead = din.read(buffer, bufferPointer = 0, BUFFER_SIZE); 
			if (bytesRead == -1) 
				buffer[0] = -1; 
		} 

		private byte read() throws IOException 
		{ 
			if (bufferPointer == bytesRead) 
				fillBuffer(); 
			return buffer[bufferPointer++]; 
		} 

		public void close() throws IOException 
		{ 
			if (din == null) 
				return; 
			din.close(); 
		}

	}

	
	public static boolean isPrime(int n) {
		if(n == 1)
		{
			return false;
		}
		for(int i = 2;i*i<=n;i++)
		{
			if(n%i == 0)
			{
				return false;
			}
		}
		return true;
	}
	
	public static int gcd(int a, int b)
	{
		if(b == 0)
		 return a;
		
		else
		return gcd(b,a%b);
	}
	
	
	public static int[] computePrefix(int arr[], int n)
	{
		int[] prefix = new int[n];
		prefix[0] = arr[0];
		for(int i = 1;i<n;i++)
		{
			prefix[i] = prefix[i-1]+arr[i];
		}
		
		return prefix;
	}
	
	public static int lcm(int a, int b)
	{
		return (a*b)/gcd(a,b);
	}
	
	public static int phi(int n)  //euler totient function
    { 
        int result = 1; 
        for (int i = 2; i < n; i++) 
            if (gcd(i, n) == 1) 
                result++; 
        return result; 
    }
	
	
	public static int[] Sort(int arr[])
	{
		
		//Heap Sort!!!
		PriorityQueue<Integer> pq = new PriorityQueue<>();
		for(int i : arr)
		{
			pq.add(i);
		}
		
		for(int i = 0;i < arr.length;i++)
		{
			arr[i] = pq.poll();
		}
		
		return arr;
	}
	
	static int LowerBound(int a[], int x) {
		  int l=-1,r=a.length;
		  while(l+1<r) {
		    int m=(l+r)>>>1;
		    if(a[m]>=x) r=m;
		    else l=m;
		  }
		  return r;
		}
	
	static int UpperBound(int a[], int x) {
	    int l=-1,r=a.length;
	    while(l+1<r) {
	       int m=(l+r)>>>1;
	       if(a[m]<=x) l=m;
	       else r=m;
	    }
	    return l+1;
	 }
	
	public static long LongGCD(long a, long b)
	{
		if(b == 0)
			return a;
		else 
			return LongGCD(b,a%b);
	}
	
	
	public static void main(String[] args) throws IOException 
	{ 
		Reader sc = new Reader();
		
		 long n=sc.nextLong();
	        int k=sc.nextInt();
	        ArrayList<Long> ans=new ArrayList<>();
	        for(long x=1;x<=(long)(Math.sqrt(n));x++)
	        {
	            if(n%x==0)
	            {
	                ans.add(x);
	                if(x!=n/x)
	                {
	                    ans.add(n / x);
	                }
	            }
	        }
	        Collections.sort(ans);
	        if(ans.size()<k)
	        {
	            out.println(-1);
	        }
	        else
	        {
	            out.println(ans.get(k-1));
	        }
		
	}
}