#include <cstdio>
#define PHI 1000005
using namespace std;
int phi[PHI];
inline long long Phi(int n){
    long long S=1;
    for(int i=2;i<=n;++i)
        phi[i]=i-1;
    for(int i=2;i<=n;++i){
        S+=2*phi[i];
        for(int j=2*i;j<=n;j+=i)
            phi[j]-=phi[i];
    }
    return S;
}
int main(){
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);
    int n;
    scanf("%d",&n);
    printf("%lld\n",Phi(n));
    fclose(stdin);fclose(stdout);
    return 0;
}