#include <cstdio>
using namespace std;
int t[1000005];
int main()
{
    int i,j,N;
    long long sol=0;
    freopen ("fractii.in","r",stdin);
    freopen ("fractii.out","w",stdout);
    scanf("%d", &N);
    for(i=1;i<=N;++i) t[i]=i;
    for(i=1;i<=N;++i)
        for(j=i*2;j<=N;j+=i) t[j]-=t[i];
    for(i=1;i<=N;++i)
        sol+=2LL*t[i];
    printf("%lld\n", sol-1);
    return 0;
}