#include <cstdio>

using namespace std;
int n, i, j;
long long phi[1000001], sum;
int main()
{
    freopen("fractii.in", "r", stdin);
    freopen("fractii.out", "w", stdout);
    scanf("%d", &n);
    for(i=2;i<=n;++i)
        phi[i]=i;
    for(i=2;i<=n;++i)
        if(phi[i]==i)
            for(j=i;j<=n;j+=i)
                phi[j]/=i, phi[j]*=(i-1);
    for(i=2;i<=n;++i)
        sum+=phi[i];
    printf("%lld\n", 1LL*(1+2*sum));
    return 0;
}