#include <bits/stdc++.h>
#define MAXN 1000000
#define INF 1000000007

long long ciur[1 + MAXN];
long long phi[1 + MAXN];
std::vector <int> prime;
int main(){
    FILE*fi,*fo;
    fi = fopen("fractii.in","r");
    fo = fopen("fractii.out","w");


    int n;
    fscanf(fi,"%d", &n);
    long long ans = 0;

    for(int i = 1; i <= n; i++) ciur[i] = INF;
    for(int i = 2; i <= n; i++){
        if(ciur[i] == INF){
            prime.push_back(i);
            ciur[i] = i;
            phi[i] = i - 1;
        }
        else{
            int j = i / ciur[i];
            if(j % ciur[i] == 0)
                phi[i] = phi[j] * i / j;
            else
                phi[i] = phi[j] * i / j * (ciur[i] - 1) / ciur[i];
        }
        for(int j = 0; j < prime.size() && i * prime[j] <= MAXN && prime[j] <= ciur[i]; j++)
            ciur[i * prime[j]] = prime[j];
        ans += phi[i];
    }
    fprintf(fo,"%lld", 2 * ans + 1);

    return 0;
}