Language: C++

#include <bits/stdc++.h>
using namespace std;

typedef long long int ll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<vi> vvi;
typedef vector<vl> vvl;
typedef vector<string>vst;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
typedef vector<pii> vii;
typedef vector<pll> vll;
typedef map<int,int> dct;

#define fastio ios_base::sync_with_stdio(false);cin.tie(0)
#define all(ct) ct.begin() , ct.end()
#define endl "\n"
#define fr(i,a) for(auto i:a)
#define f(i,a,b) for(int i=a;i<b;++i)
#define fd(i,a,b) for(int i=a;i>=b;--i)
#define pb push_back
#define in(d,v) d.find(v)!=d.end()
#define mp make_pair
#define pi 3.14159265

bool compare(pll a, pll b){
    return a.first*b.second<a.second*b.first;
}

const ll mod = 1e9+7;
const ll inf = ll(1e18);

ll modexp(ll x,ll n){
    if(n==0)return 1;
    if(n%2==0)return modexp((x*x)%mod,n/2);
    return (x*modexp((x*x)%mod,n/2))%mod;
}

int main(){
    //clock_t tm = clock();
    fastio;
    ll n,ans=0;
    cin>>n;
    if(n>9){#include <bits/stdc++.h>
using namespace std;

typedef long long int ll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<vi> vvi;
typedef vector<vl> vvl;
typedef vector<string>vst;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
typedef vector<pii> vii;
typedef vector<pll> vll;
typedef map<int,int> dct;

#define fastio ios_base::sync_with_stdio(false);cin.tie(0)
#define all(ct) ct.begin() , ct.end()
#define endl "\n"
#define fr(i,a) for(auto i:a)
#define f(i,a,b) for(int i=a;i<b;++i)
#define fd(i,a,b) for(int i=a;i>=b;--i)
#define pb push_back
#define in(d,v) d.find(v)!=d.end()
#define mp make_pair
#define pi 3.14159265

bool compare(pll a, pll b){
    return a.first*b.second<a.second*b.first;
}

const ll mod = 1e9+7;
const ll inf = ll(1e18);

ll modexp(ll x,ll n){
    if(n==0)return 1;
    if(n%2==0)return modexp((x*x)%mod,n/2);
    return (x*modexp((x*x)%mod,n/2))%mod;
}

int main(){
    //clock_t tm = clock();
    fastio;
    ll n,ans=0;
    cin>>n;
    if(n>9){
        ll x=n/10;
        cout<<(x*x+8+(n%10)*(int(log10(n))))<<endl;
        //return 0;
    }
    else{
        cout<<n<<endl;
    }
    //cout<<((clock()-tm)*1.0)/CLOCKS_PER_SEC<<endl;
}
        ll x=n/10;
        cout<<(x*x+8+(n%10)*(int(log10(n)+1))<<endl;
        //return 0;
    }
    else{
        cout<<n<<endl;
    }
    //cout<<((clock()-tm)*1.0)/CLOCKS_PER_SEC<<endl;
}

Compiler output:
a.cc:45:13: error: stray '#' in program
   45 |     if(n>9){#include <bits/stdc++.h>
      |             ^
a.cc: In function 'int main()':
a.cc:45:14: error: 'include' was not declared in this scope
   45 |     if(n>9){#include <bits/stdc++.h>
      |              ^~~~~~~
a.cc:45:23: error: 'bits' was not declared in this scope
   45 |     if(n>9){#include <bits/stdc++.h>
      |                       ^~~~
a.cc:45:28: error: 'stdc' was not declared in this scope; did you mean 'std'?
   45 |     if(n>9){#include <bits/stdc++.h>
      |                            ^~~~
      |                            std
a.cc:46:1: error: expected primary-expression before 'using'
   46 | using namespace std;
      | ^~~~~
a.cc:71:27: error: a function-definition is not allowed here before '{' token
   71 | bool compare(pll a, pll b){
      |                           ^
a.cc:78:21: error: a function-definition is not allowed here before '{' token
   78 | ll modexp(ll x,ll n){
      |                     ^
a.cc:84:9: warning: empty parentheses were disambiguated as a function declaration [-Wvexing-parse]
   84 | int main(){
      |         ^~
a.cc:84:9: note: remove parentheses to default-initialize a variable
   84 | int main(){
      |         ^~
      |         --
a.cc:84:9: note: or replace parentheses with braces to value-initialize a variable
a.cc:84:11: error: a function-definition is not allowed here before '{' token
   84 | int main(){
      |           ^
a.cc:100:46: error: invalid operands of types 'll' {aka 'long long int'} and 'const char [2]' to binary 'operator<<'
  100 |         cout<<(x*x+8+(n%10)*(int(log10(n)+1))<<endl;
      |                ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~
      |                     |
      |                     ll {aka long long int}
a.cc:100:52: error: expected ')' before ';' token
  100 |         cout<<(x*x+8+(n%10)*(int(log10(n)+1))<<endl;
      |               ~                                    ^