//Indicatorul lui Euler
//alg imbunatatit al lui pauldb
#include<cstdio>
int phi[1000000+5];
int main()
{
    FILE* fin = fopen("fractii.in","r");
    FILE* fout = fopen("fractii.out","w");

    int n;
    long long s=0;

    fscanf(fin,"%d",&n);

    for(int i=1;i<=n;++i)
        phi[i]=i;

    for(int i=2;i<=n;++i)
    {
        if(phi[i]==i)
            for(int j=i;j<=n;j+=i)
                phi[j]/=i,phi[j]*=(i-1);
        s+=phi[i];
    }

    fprintf(fout,"%lld\n",s*2+1);
    return 0;
}