#include <fstream>
#include <climits>
#pragma GCC optimize("O1")
#pragma GCC optimize("O2")
#pragma GCC optimize("O3")
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
using namespace std;
ifstream in("fractii.in");
ofstream out("fractii.out");
const long long maxN=1e6+1;
long long e[maxN];
int main()
{
    for(long long i=2;i<maxN;i++)
        e[i]=i;
    for(long long i=2;i<maxN;i++)
        if(e[i]==i)
            for(long long j=i;j<maxN;j+=i)
                e[j]=e[j]/i*(i-1);
    long long n, s=0;
    in>>n;
    for(long long i=2;i<=n;i++)
        s+=e[i];
    s=2*s+1;
    out<<s;
    return 0;
}