import java.util.*; 

class Exponential_Search 
{ 
    // Returns position of first occurrence of x in array 
    static int expoSearch(int input[], int n, int x) 
    { 
        // If x is present at firt location itself 
	if (input[0] == x) 
	    return 0; 
	
	// Find range for binary search by repeated doubling 
	int i = 1; 
	while (i < n && input[i] <= x) 
	    i = i*2; 
	
	// Call binary search for the found range. 
	return Arrays.binSearch(input, i/2, Math.min(i, n), x); 
    } 
	
    // Driver code 
    public static void main(String args[]) 
    { 
	
	int n;
	Scanner s = new Scanner(System.in);
	n = s.nextInt();
        int arr[] = new int[n];
	for (int i = 0; i < n; i++)
        {
            a[i] = s.nextInt();
        }
	int x = s.nextInt();
	int result = expoSearch(arr, arr.length, x); 
		
	System.out.println((result < 0) ? "Element is not present in array" : "index " + result); 
     } 
} 

/* 
INPUT:
n = 5
arr[] = {4, 5, 15, 80, 90}
x = 90
OUPUT:
index 4
*/

