using namespace std;

#include<iomanip>
#include<cmath>
#include<algorithm>
#include<vector>
#include<set>
#include<string>
#include<map>
#include<queue>
#include<stack>
#include<utility>
#include<cstdio>
#include<cstdlib>
#include<cassert>
#include<numeric>
#include<cstring>
#include<sstream>
#include<algorithm>
#include<deque>

const int INFI=(1LL<<30)-100;
const long long INFL=(1LL<<62)-100;
const double eps=1e-10;
const long double pi=acos(-1.0);
const int MAXN=1000100;

long long dp[MAXN];
bool prime[MAXN];
vector<int> v;

int main(){
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);

    int n;
    scanf("%d",&n);

    prime[0]=prime[1]=0;
    dp[1]=1;

    for(int i=2;i<=n;i++){
        if(!prime[i]){
            dp[i]=i-1;
            v.push_back(i);
            for(int j=2;i*j<=n;j++){
                prime[i*j]=1;
            }
        }
    }

    for(int i=4;i<=n;i++){
        if(!dp[i]){
            for(unsigned j=0;j<v.size();j++){
                if(i%v[j]==0){
                    int ax=i/v[j];
                    if(ax%v[j]==0){
                        dp[i]=dp[ax]*v[j];
                    }else{
                        dp[i]=dp[ax]*(v[j]-1);
                    }
                    break;
                }
            }
        }
    }

    long long sum=0;

    for(int i=1;i<=n;i++){
        sum+=dp[i];
    }

    printf("%lld",sum*2-1);

    return 0;
}