#include<stdio.h>
int a[2000010];
int main(){
    int N,j,n,nr,i;
    long long r=0;
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);
    scanf("%d",&N);
    for (i=2;i<=N;i++)
        a[i] = i;
    for (i=2;i<=N;i++)
        if(a[i]==i)
            for(j= i;j<=N;j+=i)
                a[j]=a[j]/i*(i-1);
    for (i=1;i<=N;i++)
        r+=a[i];
    r=r*2;
    r+=1;
    printf("%lld\n",r);
    return 0;
}