#include <cstdio>
using namespace std;
int v[1000001];

int main() {
    FILE *in,*out;
    in=fopen("fractii.in","r");
    out=fopen("fractii.out","w");
    int n,i,j;
    long long s=0;
    fscanf(in,"%d",&n);
    for (i=2; i<=n; i++)
    {
        v[i]=i;
    }
    for (i=2;i<=n;i++)
        if (v[i]==i)
        {
            for (j=i;j<=n;j+=i)
                v[j]=v[j]/i*(i-1);
        }

    for (i=2;i<=n;i++)
    {
        s=s+v[i];
    }
    s=s*2;
    s=s+1;
    fprintf(out,"%lld",s);
    return 0;
}