#include <iostream>
using namespace std;


/**
 * Find the index of the first occurrence of
 * x in arr which is of size n.
 *
 * /param x The value to look for in arr.
 * /param n The size of the array arr.
 * /param arr The array to search through.
 *
 * /return The index in the array where x first appears
 * or -1 if it does not appear.
 */

int foo(int arr[], int x, int n)
{
  int lastValue = arr[n-1];  // store the last value
  arr[n-1] = x;              // set the last value to x
  
  int i=0;
  while (arr[i] != x) {
	i++;
  }
  
  if ((i == n-1) &&        // we did not find x before the end of the array	
	  (lastValue != x)) {  // then x was not contained in arr
	i = -1;                // so we return -1
  } 

  arr[n-1] = lastValue;  // leave the array as we got it.
  return i;
}

int main()
{

  const int N = 20;
  int arr[N] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 
				 1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
    
  int x = 10;
  cout << endl 
	   << "element " << x << " is first found in our array at position " 
	   << foo(arr, x, N) << endl;

  x = 11;
  cout << endl 
	   << "element " << x << " is first found in our array at position " 
	   << foo(arr, x, N) << endl << endl;

		 return 0;  
}