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