#include <iostream>
#include <fstream>
using namespace std;
FILE *f=freopen("fractii.in","r",stdin), *g=freopen("fractii.out","w",stdout);
long long x[1000001], n, i, j, nr;
int main()
{   scanf("%lld",&n);
    for(i=2;i<=n;i++)
        x[i]=i-1;
    for(i=2;i<=n;i++)
    {
        nr+=x[i];
        for(j=2*i;j<=n;j+=i)
            x[j]-=x[i];
    }
    printf("%lld", 2*nr+1);;
    return 0;
}