【SDOI2008】仪仗队

//裸的欧拉函数
//y=kx
//求不同的k有多少
#include<bits/stdc++.h>
#define ll long long 
#define N 40010
using namespace std;
ll f[N],n,ans;
inline ll read(){
    char ch;
    bool f=false;
    ll res=0;
    while (((ch=getchar())<'0'||ch>'9')&&ch!='-');
    if (ch=='-')
        f=true;
    else 
        res=ch-'0';
    while ((ch=getchar())>='0'&&ch<='9')
        res=(res<<3)+(res<<1)+ch-'0';
    return f?~res+1:res;
}
int main(){
    n=read();
    if (n==1){
        printf("0
");
        return 0;
    }
    for (int i=1;i<=n;i++)
        f[i]=i;
    for (int i=2;i<=n;i++)
        if (f[i]==i)
            for (int j=i;j<=n;j+=i)
                f[j]=f[j]/i*(i-1);
    ans=2;
    for(int i=2;i<n;++i)
        ans+=f[i]*2;
    printf("%lld
",ans+1);
    return 0;
}