#include<bits/stdc++.h>

using namespace std;

int fi[1000002],n;

void Phi()
{
    int i, j;
    for(i = 1; i <= 1000000; i++)
        fi[i] = i - 1;
    for(i = 2; i <= 1000000; i++)
        for(j = i + i; j <= 1000000; j += i)
            fi[j] -= fi[i];

}

int main()
{
    long long cnt=0;
    ifstream fin("fractii.in");
    ofstream fout("fractii.out");
    fin>>n;
    fin.close();
    Phi();
    for(int i=2;i<=n;i++)
        cnt+=fi[i];
    cnt*=2;
    cnt++;
    fout<<cnt;
    fout.close();
    return 0;
}