#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);
for(i=2;i<=n;i++){
f[i]=i-1;
}
for(i=2;i<=n;i++){
s+=f[i];
for(j=i+i;j<=n;j+=i){
f[j]=f[j]-f[i];
}
}
s*=2;
printf("%lld\n",++s);
return 0;
}