#include <cstdio>
FILE *g=fopen("fractii.in","r");
FILE *z=fopen("fractii.out","w");
using namespace std;
int main()
{
    long long int prim[1000099],n,i,j,ct=0;
    fscanf(g,"%llu",&n);
    for(i=1;i<=n;i++)
    prim[i]=i-1;
    for(i=2;i<=n;i++)
    {
        for(j=i+i;j<=n;j+=i)
        prim[j]-=prim[i];
    }
    for(i=1;i<=n;i++)
    ct+=2*prim[i];
    fprintf(z,"%llu",ct+1);
    return 0;
}