#include <cstdio>

int main(void)
{
    freopen("fractii.in", "r", stdin);
    freopen("fractii.out", "w", stdout);
    int nV; long long nC;
    scanf("%d", &nV);
    nC = 1 + (nV - 1) * 2;
    for(int i(2); i <= nV; i++)
    {
        if(i%2 > 0)
        {
            int k = 0,j = 1;
            while(i * j <= nV)
                k++, j++;
            nC += (nV - i + 1 - k) * 2;
        }
        else
        {
            int k = 0, j = 0;
            while(i + j <= nV)
                k++, j += 2;
            nC += (nV - i + 1 - k) * 2;
        }
    }
    printf("%llu", nC);
    return 0;
}