#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;
using i8=int8_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);}
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;}
  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...>>>;
}
namespace my{
ll totient_prime_pow(ll p,i8,ll pk){return(pk-pk/p);}
template<class T>struct linear_sieve{
  T n;
  vec<int>lpf;
  vec<i8>lpf_ord;
  vec<int>lpf_pow;
  vec<int>lpf_pow_except;
  vec<int>primes;
  linear_sieve(T n):n(n),lpf(n+1,-1),lpf_ord(n+1),lpf_pow(n+1),lpf_pow_except(n+1){
    lpf[1]=lpf_ord[1]=lpf_pow[1]=lpf_pow_except[1]=1;

    fo(i,2,n+1){
      if(lpf[i]==-1)primes.eb(lpf[i]=i);

      fe(primes,p){
        if(p*i>n||p>lpf[i])break;
        lpf[p*i]=p;
      }

      int j=i/lpf[i];
      lpf_ord[i]=lpf_ord[j]*(lpf[i]==lpf[j])+1;
      lpf_pow[i]=((lpf_pow[j]-1)*(lpf[i]==lpf[j])+1)*lpf[i];
      lpf_pow_except[i]=i/lpf_pow[i];
    }
  }
  auto multiplicative_function_enumerate(const auto&f)const{
    vec<T>r(n+1);
    r[1]=1;
    fo(i,2,n+1)r[i]=f(lpf[i],lpf_ord[i],lpf_pow[i])*r[lpf_pow_except[i]];
    return r;
  }
  auto totient_enumerate()const{return multiplicative_function_enumerate(totient_prime_pow);}
};
}
namespace my{entry
void main(){
  LL(N);

  auto Phi=linear_sieve<int>(N).totient_enumerate().zeta();

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