Language: C++

#include <bits/stdc++.h>
#define int long long
#define rep(i,n) for(int i=0;i<n;++i)
using namespace std;
int main{
  int a;
  int c=0;
  int e=0;
  cin>>a;
  vector<int> b(a);
  rep(i,a)
  cin>>b.at(i);
  rep(i,b.size()){
    if(b.at(i)<400){
      int d=0;
        d++;
      if(d==1)
        c++;
        }
  if(400<=b.at(i)&&b.at(i)<800){
      int d=0;
        d++;
      if(d==1)
        c++;
        }
  if(800<=b.at(i)&&b.at(i)<1200){
      int d=0;
        d++;
      if(d==1)
        c++;
        }
  if(1200<=b.at(i)&&b.at(i)<1600){
      int d=0;
        d++;
      if(d==1)
        c++;
        }
  if(1600<=b.at(i)&&b.at(i)<2000){
      int d=0;
        d++;
      if(d==1)
        c++;
        }
  if(2000<=b.at(i)&&b.at(i)<2400){
      int d=0;
        d++;
      if(d==1)
        c++;
        }
  if(2400<=b.at(i)&&b.at(i)<2800){
      int d=0;
        d++;
      if(d==1)
        c++;
        }
  if(2800<=b.at(i)&&b.at(i)<3200){
      int d=0;
        d++;
      if(d==1)
        c++;
        }
  if(3200<b.at(i))
    e++;
  }
  cout<<c;
  cout<<c+e;

Compiler output:
a.cc:5:5: error: cannot declare '::main' to be a global variable
    5 | int main{
      |     ^~~~
a.cc:2:13: error: expected primary-expression before 'long'
    2 | #define int long long
      |             ^~~~
a.cc:6:3: note: in expansion of macro 'int'
    6 |   int a;
      |   ^~~
a.cc:2:13: error: expected '}' before 'long'
    2 | #define int long long
      |             ^~~~
a.cc:6:3: note: in expansion of macro 'int'
    6 |   int a;
      |   ^~~
a.cc:5:9: note: to match this '{'
    5 | int main{
      |         ^
a.cc:9:3: error: 'cin' does not name a type
    9 |   cin>>a;
      |   ^~~
a.cc:10:17: error: 'a' was not declared in this scope
   10 |   vector<int> b(a);
      |                 ^
a.cc:3:18: error: expected unqualified-id before 'for'
    3 | #define rep(i,n) for(int i=0;i<n;++i)
      |                  ^~~
a.cc:11:3: note: in expansion of macro 'rep'
   11 |   rep(i,a)
      |   ^~~
a.cc:11:7: error: 'i' does not name a type
   11 |   rep(i,a)
      |       ^
a.cc:3:30: note: in definition of macro 'rep'
    3 | #define rep(i,n) for(int i=0;i<n;++i)
      |                              ^
a.cc:3:34: error: expected unqualified-id before '++' token
    3 | #define rep(i,n) for(int i=0;i<n;++i)
      |                                  ^~
a.cc:11:3: note: in expansion of macro 'rep'
   11 |   rep(i,a)
      |   ^~~
a.cc:3:18: error: expected unqualified-id before 'for'
    3 | #define rep(i,n) for(int i=0;i<n;++i)
      |                  ^~~
a.cc:13:3: note: in expansion of macro 'rep'
   13 |   rep(i,b.size()){
      |   ^~~
a.cc:13:7: error: 'i' does not name a type
   13 |   rep(i,b.size()){
      |       ^
a.cc:3:30: note: in definition of macro 'rep'
    3 | #define rep(i,n) for(int i=0;i<n;++i)
      |                              ^
a.cc:3:34: error: expected unqualified-id before '++' token
    3 | #define rep(i,n) for(int i=0;i<n;++i)
      |                                  ^~
a.cc:13:3: note: in expansion of macro 'rep'
   13 |   rep(i,b.size()){
      |   ^~~
a.cc:65:3: error: 'cout' does not name a type
   65 |   cout<<c;
      |   ^~~~
a.cc:66:3: error: 'cout' does not name a type
   66 |   cout<<c+e;
      |   ^~~~