#include <cstdio>
using namespace std;
int main()
{
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);
    int c[1000002],n,i,j;
    long long nr=0;
    scanf("%d",&n);
    for(i=2; i<=n; i++)
        c[i]=i-1;
    for(i=2; i<=n; i++)
    {
        nr+=c[i];
        for(j=i+i; j<=n; j=j+i)
            c[j]-=c[i];
    }
    nr=nr*2+1;
    printf("%lld",nr);
    return 0;
}