#include <bits/stdc++.h>
using namespace std;
ifstream in("fractii.in");
ofstream out("fractii.out");
int n,i,j,dv[1000001],nj;
bool p[1000001];
long long s;
int main()
{
    in>>n;
    for(i=2,s=n; i<=n; ++i,nj=0)
    {
        if(p[i]==0)
        {
            p[i]=1;
            ++dv[i];
            ++nj;
            for(j=2; j*i<=n; ++j)
            {
                if(p[i*j]==0)
                    ++dv[i];
                ++nj;
            }
            for(j=2; j*i<=n; ++j)
            {
                if(p[i*j]==0)
                    dv[i*j]+=nj,p[i*j]=1;
                else
                    dv[i*j]+=dv[i];
            }
            s+=n-nj;
        }
        else s+=n-dv[i];
    }
    out<<s;
}


/*



10
dv[2]=5;
dv[4]=5;
dv[6]=7;
dv[8]=5;
dv[10]=5;
dv[5]=1;
dv[3]=2;
dv[9]=
0 1 1 1 0 1 0 1 1 1
1 2 3 4 5 6 7 8 9 10

s=

*/