#include <cstdio>
#include <cmath>
long long v[1000005],w[1000005];
int main()
{
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);
    scanf("%d",&n);
    int i,ii,j,htc=0; v[1]=1;
    for (i=2;i<=n;++i)
        for (j=i+i; j<=n; j+=i)
            ++v[j];
    w[1]=1; w[2]=3;
    for (i=3;i<=n;++i)
        w[i]=w[i-1]+(i-v[i]-1)*2;
    printf("%d",w[n]);
    return 0;
}