#include<bits/stdc++.h>
using namespace std;
int n,i,j,v[1000005];
long long nr;
int main()
{
    freopen("fractii.in", "r", stdin);
    freopen("fractii.out", "w", stdout);
    scanf("%d", &n);
    for (i=2;i<=n;i++)
        v[i] = i-1;
    for (i=2;i<=n;i++)
    {
        nr += v[i];
        for (j=i*2;j<=n;j+=i)
            v[j] -= v[i];
    }
    printf("%lld", 2*nr+1);
    return 0;
}