#include<cstdio>
int phi[1000000+5];
int main()
{
    FILE* fin = fopen("fractii.in","r");
    FILE* fout = fopen("fractii.out","w");
    int n;
    fscanf(fin,"%d",&n);
    for(int i=1;i<=n;++i)
        phi[i]=i-1;
    for(int i=2;i<=n;++i)
        for(int j=2*i;j<=n;j+=i)
            phi[j]-=phi[i];
    long long s=0;
    for(int i=1;i<=n;++i)
        s+=phi[i];
    s=(s<<1)+1;
    fprintf(fout,"%lld\n",s);
    return 0;
}