#include <iostream>   //C++ example
#include <cstdlib>
using namespace std;

int main(int argc, char **argv)
{
	if (argc != 2) {
		cerr << argv[0] << ": requires one command line argument\n";
		return EXIT_FAILURE;
	}

	int sum = 0;
	const int n = atoi(argv[1]);

	for (int i = 1; i <= n; ++i) {
		sum += i;
	}

	cout << "The sum of the numbers from 1 to " << n << " is " << sum << ".\n";
	return EXIT_SUCCESS;
}