#include<stdio.h>
#define maxim 1000000
using namespace std;
int nu[maxim+3];
int main()
{   int i,n,j;
    for(i=2;i<=maxim;++i) nu[i]=i;
    for(i=2;i<=maxim;++i)
        if(nu[i]==i)
            for(j=i;j<=maxim;j+=i){
                nu[j]/=i;nu[j]*=(i-1);
            }
    freopen("fractii.in","r",stdin);
    scanf("%d",&n);fclose(stdin);
    long long sol=0;
    for(i=2;i<=n;++i) sol+=(long long) nu[i];
    freopen("fractii.out","w",stdout);
    printf("%lld",2*sol+1);
    fclose(stdout);
    return 0;
}