#include <cstdio>
using namespace std;
int v[1000000];
int main()
{
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);
    int n;
    scanf("%d",&n);
    long long sum=0;
    for(int i=1; i<=n; ++i)
        v[i]=i;
    for(int i=2; i<=n; ++i)
        if(v[i]==i)
            for(int j=i; j<=n; j+=i)
                v[j]-=v[j]/i;
    for(int i=1;i<=n;++i)
        sum+=v[i];
    printf("%lld",sum*2-1);
    return 0;
}