#include<cstdio>
using namespace std;
const int LIM=1000010; int n;
long long v[LIM], sol=0;
int main(){
    FILE *in=fopen("fractii.in","r"), *out=fopen("fractii.out","w");
    int n;
    fscanf(in, "%d\n", &n);
    for (int i=1;i<=n;i++) v[i]=i;
        for (int i=2;i<=n;i++){
            if (v[i]==i)
                for (int j=i;j<=n;j+=i) {v[j] /=i; v[j] *= (i-1);}
            sol+=v[i]*2;
        }
    fprintf(out, "%lld\n", sol+1);
    return 0;
}