#include<cstdio>
int i,n,j,phi[1000010];
long long SOL;
int main()
{
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);
    scanf("%d",&n);
    for(i=1;i<=n;i++)phi[i]=i-1;
    for(i=2;i<=n;i++)
    {
        //if(phi[i]!=i-1)continue;
        for(j=i+i;j<=n;j+=i)phi[j]-=phi[i];
    }
    for(i=1;i<=n;i++)SOL+=(long long)phi[i]+phi[i];
    printf("%lld\n",SOL+1);
    return 0;
}