#include<stdio.h>
int i,j,n;
long long v[1000001],s;
int main(){
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);
    scanf("%d",&n);
    for(i=2;i<=n;i++)
        v[i]=i;
    for(i=2;i<=n;i++)
        if(v[i]==i){
            for(j=i;j<=n;j+=i)
                v[j]=v[j]/i*(i-1);
        }
    s=0;
    for(i=2;i<=n;i++)
        s+=v[i];
    printf("%lld",s*2+1);
    return 0;
}