#include <cstdio>

using namespace std;
const int NMAX=500000;
int c[NMAX+5],prim[100000];
int putere(int a,int b)
{
    int prod=1,i;
    for(i=1; i<=b-1; i++)
        prod*=a;
    return prod*(a-1);
}
int main()
{
  freopen("fractii.in","r",stdin);
  freopen("fractii.out","w",stdout);
    int n,i,fi,j,aux,d,k=0,put;
    long long sum=0;
    c[1]=1;
    for(i=2; i<=NMAX; i++)
        if(c[i]==0)
            for(j=2*i; j<=NMAX; j+=i)
                c[j]=1;
    for(i=2; i<=NMAX; i++)
        if(!c[i])
            prim[++k]=i;
    scanf("%d",&n);
    for(i=n; i>=2; i--)
    {
        aux=i;
        fi=1;
        for(d=1; d<=k; d++)
        {
            if(prim[d]>i)
                break;
            put=0;
            while(aux%prim[d]==0)
            {
                put++;
                aux/=prim[d];
            }
            if(put==1)
                fi*=prim[d]-1;
            if(put>=2)
                fi*=putere(prim[d],put);
        }
        sum+=2*fi;
    }
    printf("%lld",sum+1);
    return 0;
}