#include <iostream>
#include <cstdlib>
using namespace std;

//Search the array for a pair of consecutive equal values.
//ptrdiff_t holds the difference between the values of two pointers.

int main()
{
	int a[] {0, 10, 20, 30, 40, 40, 50, 60};
	const size_t n {size(a)};   //the number of elements in the array
				    //As usual, the last element is a[n-1].
				    //The next-to-last element is a[n-2].

	for (const int *p {a}; p < a + n - 2; ++p) {
		if (p[0] == p[1]) {
			const ptrdiff_t i {p - a};
			cout << "a[" << i   << "] = " << p[0] << "\n";
			cout << "a[" << i+1 << "] = " << p[1] << "\n";
		}
	}

	return EXIT_SUCCESS;
}