#include<cstdio>
using namespace std;
int phi[1000010];
int main(){
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);
    int n,i,j;
    long long answer=0;
    scanf("%d",&n);
    for(i=1;i<=n;i++)
        phi[i]=i;
    for(i=2;i<=n;i++)
        if(phi[i]==i)
            for(j=1;j<=n/i;j++){
                phi[i*j]=phi[i*j]*(i-1);
                phi[i*j]/=i;
            }
    for(i=1;i<=n;i++)
        answer+=phi[i];
    printf("%lld",2*answer-1);
    return 0;
}