Language: C++

=#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
ll mod = 1000000007;
#define pll pair<ll,ll>
#define pii pair<int32_t,int32_t>
#define loop(i,n) for(int64_t i=0; i<n; i++)
#define loop1(i,a,b) for(int64_t i=a; i<=b; i++)
#define rloop(i,n) for(int64_t i=n-1; i>=0; i--) 
#define rloop1(i,a,b) for(int64_t i=a; i>=b; i--) 
#define fast_io ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
#define print(val) cout << #val << ": " << val << "\n";
#define print_c(a) cout<<#a<<": ";for(auto it=begin(a);it!=end(a);it++)cout<<*it<<" ";cout<<"\n";
#define fill(c,v) fill(begin(c),end(c),v);
template <typename T> T flip(T val) {reverse(begin(val),end(val)); return val;}

vector<ll> vec;

int main() {
  fast_io
  ll n; cin >> n;
  vec.resize(n+1);
  fill(vec,0);

  ll ans=0;
  loop1(i,1,n) {
    for(ll j=i; j<=n; j+=i) {
      vec[j]++;
    }
    ans = ans + (i*vec[i]);
  }
  cout << ans << "\n";
}

Compiler output:
a.cc:1:2: error: stray '#' in program
    1 | =#include <bits/stdc++.h>
      |  ^
a.cc:1:1: error: expected unqualified-id before '=' token
    1 | =#include <bits/stdc++.h>
      | ^
a.cc:17:1: error: 'vector' does not name a type
   17 | vector<ll> vec;
      | ^~~~~~
a.cc: In function 'int main()':
a.cc:11:17: error: 'ios_base' has not been declared
   11 | #define fast_io ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
      |                 ^~~~~~~~
a.cc:20:3: note: in expansion of macro 'fast_io'
   20 |   fast_io
      |   ^~~~~~~
a.cc:11:51: error: 'cin' was not declared in this scope
   11 | #define fast_io ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
      |                                                   ^~~
a.cc:20:3: note: in expansion of macro 'fast_io'
   20 |   fast_io
      |   ^~~~~~~
a.cc:11:59: error: 'NULL' was not declared in this scope
   11 | #define fast_io ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
      |                                                           ^~~~
a.cc:20:3: note: in expansion of macro 'fast_io'
   20 |   fast_io
      |   ^~~~~~~
a.cc:1:1: note: 'NULL' is defined in header '<cstddef>'; this is probably fixable by adding '#include <cstddef>'
  +++ |+#include <cstddef>
    1 | =#include <bits/stdc++.h>
a.cc:11:66: error: 'cout' was not declared in this scope
   11 | #define fast_io ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
      |                                                                  ^~~~
a.cc:20:3: note: in expansion of macro 'fast_io'
   20 |   fast_io
      |   ^~~~~~~
a.cc:22:3: error: 'vec' was not declared in this scope
   22 |   vec.resize(n+1);
      |   ^~~
a.cc:14:24: error: 'begin' was not declared in this scope
   14 | #define fill(c,v) fill(begin(c),end(c),v);
      |                        ^~~~~
a.cc:23:3: note: in expansion of macro 'fill'
   23 |   fill(vec,0);
      |   ^~~~
a.cc:14:33: error: 'end' was not declared in this scope
   14 | #define fill(c,v) fill(begin(c),end(c),v);
      |                                 ^~~
a.cc:23:3: note: in expansion of macro 'fill'
   23 |   fill(vec,0);
      |   ^~~~
a.cc:14:19: error: 'fill' was not declared in this scope
   14 | #define fill(c,v) fill(begin(c),end(c),v);
      |                   ^~~~
a.cc:23:3: note: in expansion of macro 'fill'
   23 |   fill(vec,0);
      |   ^~~~
a.cc:8:26: error: 'int64_t' was not declared in this scope
    8 | #define loop1(i,a,b) for(int64_t i=a; i<=b; i++)
      |                          ^~~~~~~
a.cc:26:3: note: in expansion of macro 'loop1'
   26 |   loop1(i,1,n) {
      |   ^~~~~
a.cc:1:1: note: 'int64_t' is defined in header '<cstdint>'; this is probably fixable by adding '#include <cstdint>'
  +++ |+#include <cstdint>
    1 | =#include <bits/stdc++.h>
a.cc:26:9: error: 'i' was not declared in this scope
   26 |   loop1(i,1,n) {
      |         ^
a.cc:8:39: note: in definition of macro 'loop1'
    8 | #define loop1(i,a,b) for(int64_t i=a; i<=b; i++)
      |                                       ^