#include<bits/stdc++.h>
#if __has_include(<atcoder/all>)
#endif
using namespace std;
#define eb emplace_back
#define LL(...) ll __VA_ARGS__;lin(__VA_ARGS__)
#define FO(n) for(ll IJK=n;IJK-->0;)
#define fo(i,...) for(auto[i,i##stop,i##step]=for_range<ll>(0,__VA_ARGS__);i<i##stop;i+=i##step)
#define of(i,...) for(auto[i,i##stop,i##step]=for_range<ll>(1,__VA_ARGS__);i>=i##stop;i+=i##step)
#define fe(a,e,...) for(auto&&__VA_OPT__([)e __VA_OPT__(,__VA_ARGS__]):a)
#define defpp template<ostream&o=cout>void pp(const auto&...a){[[maybe_unused]]const char*c="";((o<<c<<a,c=" "),...);o<<'\n';}void epp(const auto&...a){pp<cerr>(a...);}
#define entry defpp void main();void main2();}int main(){my::io();my::main();}namespace my{
namespace my{
void io(){cin.tie(nullptr)->sync_with_stdio(0);cout<<fixed<<setprecision(15);}
using ll=long long;
using ui32=uint32_t;
using ui64=uint64_t;
template<class T>constexpr auto for_range(T s,T b){T a=0;if(s)swap(a,b);return array{a-s,b,1-s*2};}
template<class T>constexpr auto for_range(T s,T a,T b,T c=1){return array{a-s,b,(1-s*2)*c};}
void lin(auto&...a){(cin>>...>>a);}
auto ceil(auto x,auto y){if(y<0)x=-x,y=-y;return x<=0?x/y:(x-1)/y+1;}
auto max(auto...a){return max(initializer_list<common_type_t<decltype(a)...>>{a...});}
constexpr ui64 kth_root_floor(ui64 a,ll k){
  if (k==1)return a;
  auto within=[&](ui32 x){ui64 t=1;FO(k)if(__builtin_mul_overflow(t,x,&t))return false;return t<=a;};

  ui64 r=0;
  of(i,sizeof(ui32)*CHAR_BIT)if(within(r|(1u<<i)))r|=1u<<i;
  return r;
}
constexpr auto sqrt_floor(auto x){return kth_root_floor(x,2);}
template<class...A>using pack_back_t=tuple_element_t<sizeof...(A)-1,tuple<A...>>;
}
namespace my{
template<class V>concept vectorial=is_base_of_v<vector<typename remove_cvref_t<V>::value_type>,remove_cvref_t<V>>;
template<class V>struct vec;
template<int D,class T>struct hvec_helper{using type=vec<typename hvec_helper<D-1,T>::type>;};
template<class T>struct hvec_helper<0,T>{using type=T;};
template<int D,class T>using hvec=hvec_helper<D,T>::type;
template<class V>struct vec:vector<V>{
  using vector<V>::vector;
  ll size()const{return vector<V>::size();}
  auto&emplace_back(auto&&...a){vector<V>::emplace_back(std::forward<decltype(a)>(a)...);return*this;}
  auto pop_back(){auto r=this->back();vector<V>::pop_back();return r;}
  vec zeta()const{vec v=*this;if constexpr(vectorial<V>){ }fo(i,v.size()-1)v[i+1]+=v[i];return v;}
};
template<class...A>requires(sizeof...(A)>=2)vec(const A&...a)->vec<hvec<sizeof...(A)-2,pack_back_t<A...>>>;
template<class T=int>auto iota(ll l,ll r=0){if(l>r)swap(l,r);vec<T>v(r-l);std::iota(v.begin(),v.end(),l);return v;}
}
namespace my{
template<class T>auto prime_enumerate(T n){
  vec<bool>sieve(n/3+1,1);
  for(T p=5,d=4,i=1,rn=sqrt_floor(n);p<=rn;p+=d=6-d,i++){
    if(!sieve[i])continue;
    for(T q=(p*p)/3,r=d*p/3+(d*p%3==2),s=p*2;q<sieve.size();q+=r=s-r)sieve[q]=0;
  }
  vec<T>r{2,3};
  for(T p=5,d=4,i=1;p<=n;p+=d=6-d,i++)if(sieve[i])r.eb(p);
  while(r.size()&&r.back()>n)r.pop_back();
  return r;
}
}
namespace my {
template<class T>auto interval_totient_enumerate(ll L,ll R){
  auto remain=iota<T>(L,R);
  auto res=iota<T>(L,R);
  fe(prime_enumerate(sqrt_floor(R-1)),p){
    fo(i,max(ceil(L,p)*p,p),R,p){
      while(remain[i-L]%p==0)remain[i-L]/=p;
      res[i-L]-=res[i-L]/p;
    }
  }
  fo(i,L,R)if(remain[i-L]>1)res[i-L]-=res[i-L]/remain[i-L];
  return res;
}
}
namespace my{entry
void main(){
  LL(N);
  auto Phi=interval_totient_enumerate<int>(0,N+1).zeta();

  ll ans=0;
  fo(g,1,N+1)ans+=Phi[sqrt_floor(N/g)]-1;
  pp(ans*2+N);
}}