namespace ALGA {
	public class PyramidProblem {
		public static int triangular_number_recursive(int n) {
			if (n <= 0) return 0;
			return n + triangular_number_recursive(n - 1);
		}

		public static int triangular_number_iterative(int n) {
			if (n <= 0) return 0;
			int total = 0;
			for (int i = 1; i <= n; i++)
				total += i;
			return total;
		}

		public static int triangular_number_function(int n) {
			if (n <= 0) return 0;
			return (n + 1) * n / 2;
		}
	}
}