#include<cstdio>
using namespace std;
int N,A[1000010];
long long rez;
int main()
{
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);
    scanf("%d",&N);
    for (int i=2;i<=N;++i) A[i]=i-1;
    for (int i=2;i<=N;++i)
    {
        rez+=A[i];
        for (int j=2*i;j<=N;j+=i) A[j]-=A[i];
    }
    printf("%lld\n",2*rez+1);
    fclose(stdin); fclose(stdout);
    return 0;
}