#include <bits/stdc++.h>
using namespace std;
bitset <1000001> v;
double v2[1000001];
int main()
{
    ifstream fin("fractii.in");
    ofstream fout("fractii.out");
    v[1] = v[0] = 1;
    long long cnt = 0,n,sum = 0;
    fin >> n;
    for (int i = 1;i <= n; i++)
    	v2[i]=i;
    for (double i = 2; i <= n; i = i + 1)
    	if (v[i] == 0) {
        	v2[(int)(i)]=i-1;
            for (double j = i + i; j <= n; j += i)
                v[(int)(j)] = 1, v2[(int)(j)] = v2[(int)(j)] * (i-1)/i;
        }
    for (int i = 2;i <= n; i++)
        sum = sum + (v2[i] * 2);
    fout << sum + 1;
    return 0;
}