#include <stdio.h>
#include <stdlib.h>

long gen(long N)
{
	long i, j;
	long sum = N;
	for (i = 2; i <= N; i++)
	{
		sum++;
		for (j = 2; j <= N; j++)
		{
			if (j % i == 0)
			{
				sum++;
			}
		}
	}
	return sum;
}

int main()
{
	FILE* in = fopen("fractii.in", "rt");
	FILE* out = fopen("fractii.out", "wt");
	long N, nr;
	fscanf(in, "%ld", &N);
	nr = gen(N);
	fprintf(out, "%ld\n", nr);
	fclose(in);
	fclose(out);
	return 0;
}