#include<bits/stdc++.h>
using namespace std;
#define MAXN 50010
#define LL long long
int mu[MAXN],prime[MAXN],tot,qz[MAXN],n;
bitset<MAXN> vis;
void getmu()
{
    int i,j;
    mu[1]=1;
    for(i=2;i<=n;i++)
    {
        if(vis[i]==0)
        {
            prime[++tot]=i;
            mu[i]=-1;
        }
        for(j=1;j<=tot&&prime[j]*i<=n;j++)
        {
            vis[prime[j]*i]=1;
            if(i%prime[j]==0)
            {
                mu[prime[j]*i]=0;
                break;
            }
            mu[prime[j]*i]=-mu[i];
        }
    }
}
void Qz()
{
    for(int i=1;i<=n;i++)qz[i]=qz[i-1]+mu[i];
}
LL calc()
{
    int d,pos;
    LL sum=0;
    for(d=1;d<=n;d=pos+1)
    {
        pos=n/(n/d);
        sum+=(LL)(qz[pos]-qz[d-1])*(n/d)*(n/d);
    }
    return sum;
}
int main()
{
    freopen("sendtable.in","r",stdin);
    freopen("sendtable.out","w",stdout);
    scanf("%d",&n);
    getmu();
    Qz();
    printf("%lld",calc());
    fclose(stdin);
    fclose(stdout);
    return 0;
}