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

/* Output these 10 lines:
 
0
01
012
0123
01234
012345
0123456
01234567
012345678
0123456789

The variable "row" does two jobs:
1.  It keeps count of which row you're currently outputting, so you don't output
too many rows.
2.  It also controls the length (i.e., the number of X's) of each row.
*/

int main()
{
	int nrows {10};

	for (int row {0}; row < nrows; ++row) {
		//Inner loop outputs a row of row+1 digits, all on same line.
		for (int col {0}; col <= row; ++col) {
			cout << col;
		}
		cout << "\n";
	}

	return EXIT_SUCCESS;
}