#include <stdio.h>

int e[1000001];
int main()
{
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);
    int n,i,j;
    long long s=0;
    scanf("%d",&n);

    for(i=1;i<=n;i++) e[i]=i;

    for(i=2;i<=n;i++)
        if(e[i]==i)
            for(j=i;j<=n;j=j+i) e[j]*=i-1,e[j]/=i;

    for(i=1;i<=n;i++) s+=e[i];

    s=s*2-1;

    printf("%lld\n",s);
}