Language: C++

#include<bits/stdc++.h>
#define ls(x) (x)<<1
#define rs(x) (x)<<1|1
#define lson l,m,rt<<1
#define rson m+1,r,rt<<1|1
#define ll rt<<1
#define rr rt<<1|1
#define PI acos(-1)
#define MM int m=(l+r)>>1;
#define fu(i,r,t) for(int i=r;i<=t;i++)
#define fd(i,r,t) for(int i=r;i>=t;i--)
#define IOS ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define int long long
#define endl '\n'
#define lcm(a,b) (a*b)/__gcd(a,b)
#define Case(i,ans) cout<<"Case "<<i<<": "<<ans<<endl;
#define cp(i,ans) printf("%.if",ans);
#define cpp(i,ans) cout<<setprecision(i)<<fixed<<ans<<endl;
#define ppb pop_back
#define ppf pop_front
#define pb push_back
#define pf push_front
#define pq priority_queue
#define lowbit(x) (x)&(-x)
#define all(V) V.begin(),V.end()
#define ms multiset
#define mod(x) (x)%mo_num
#define vc vector
#define vct vector<int>
#define fa(i,V) for(auto i:V)
#define out(i) cout<<i<<endl;
#define fi first
#define sc second
#define fun(i) fu(i,1,n)
#define fut(i) fu(i,1,t)
#define fum(i) fu(i,1,m)
#define ld long double
//#define P pair<int,int>
using namespace std;
const int INF=LLONG_MAX;
const int maxn=1e6+5;
const int mo_num=1e9+7;
int n,m,a[maxn],b[maxn],ans;

int32_t main()
{
    IOS#include<bits/stdc++.h>
#define ls(x) (x)<<1
#define rs(x) (x)<<1|1
#define lson l,m,rt<<1
#define rson m+1,r,rt<<1|1
#define ll rt<<1
#define rr rt<<1|1
#define PI acos(-1)
#define MM int m=(l+r)>>1;
#define fu(i,r,t) for(int i=r;i<=t;i++)
#define fd(i,r,t) for(int i=r;i>=t;i--)
#define IOS ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define int long long
#define endl '\n'
#define lcm(a,b) (a*b)/__gcd(a,b)
#define Case(i,ans) cout<<"Case "<<i<<": "<<ans<<endl;
#define cp(i,ans) printf("%.if",ans);
#define cpp(i,ans) cout<<setprecision(i)<<fixed<<ans<<endl;
#define ppb pop_back
#define ppf pop_front
#define pb push_back
#define pf push_front
#define pq priority_queue
#define lowbit(x) (x)&(-x)
#define all(V) V.begin(),V.end()
#define ms multiset
#define mod(x) (x)%mo_num
#define vc vector
#define vct vector<int>
#define fa(i,V) for(auto i:V)
#define out(i) cout<<i<<endl;
#define fi first
#define sc second
#define fun(i) fu(i,1,n)
#define fut(i) fu(i,1,t)
#define fum(i) fu(i,1,m)
#define ld long double
//#define P pair<int,int>
using namespace std;
const int INF=LLONG_MAX;
const int maxn=1e6+5;
const int mo_num=1e9+7;
int n,m,a[maxn],b[maxn],ans;
int a；
int32_t main()
{
    IOS
    cin>>a;
    cout<<a*a*3;
    return 0;
}
    cin>>a;
    cout<<a*a*3;
    return 0;
}

Compiler output:
a.cc:47:8: error: stray '#' in program
   47 |     IOS#include<bits/stdc++.h>
      |        ^
a.cc: In function 'int32_t main()':
a.cc:47:9: error: 'include' was not declared in this scope
   47 |     IOS#include<bits/stdc++.h>
      |         ^~~~~~~
a.cc:47:17: error: 'bits' was not declared in this scope
   47 |     IOS#include<bits/stdc++.h>
      |                 ^~~~
a.cc:47:22: error: 'stdc' was not declared in this scope; did you mean 'std'?
   47 |     IOS#include<bits/stdc++.h>
      |                      ^~~~
      |                      std
a.cc:85:1: error: expected primary-expression before 'using'
   85 | using namespace std;
      | ^~~~~
a.cc:91:1: error: expected initializer before 'int32_t'
   91 | int32_t main()
      | ^~~~~~~
a.cc:98:8: error: no match for 'operator>>' (operand types are 'std::istream' {aka 'std::basic_istream<char>'} and 'long long int [1000005]')
   98 |     cin>>a;
      |     ~~~^~~
      |     |    |
      |     |    long long int [1000005]
      |     std::istream {aka std::basic_istream<char>}
In file included from /usr/include/c++/14/sstream:40,
                 from /usr/include/c++/14/complex:45,
                 from /usr/include/c++/14/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:127,
                 from a.cc:1:
/usr/include/c++/14/istream:170:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(bool&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  170 |       operator>>(bool& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:170:7: note:   conversion of argument 1 would be ill-formed:
a.cc:98:10: error: cannot bind non-const lvalue reference of type 'bool&' to a value of type 'long long int*'
   98 |     cin>>a;
      |          ^
/usr/include/c++/14/istream:174:7: note: candidate: 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(short int&) [with _CharT = char; _Traits = std::char_traits<char>]' (near match)
  174 |       operator>>(short& __n);
      |       ^~~~~~~~
/usr/include/c++/14/istream:174:7: note:   conversion of argument 1 would be ill-formed:
a.cc:98:10: error: invalid conversion from 'long long int*' to 'short int' [-fpermissive]
   98 |     cin>>a;
      |          ^
      |          |
      |          long long int*
a.cc:98:10: error: cannot bind rvalue '(short int)((long long int*)(& a))' to 'short int&'
/usr/include/c++/14/istream:177:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(short unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  177 |       operator>>(unsigned short& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:177:7: note:   conversion of argument 1 would be ill-formed:
a.cc:98:10: error: invalid conversion from 'long long int*' to 'short unsigned int' [-fpermissive]
   98 |     cin>>a;
      |          ^
      |          |
      |          long long int*
a.cc:98:10: error: cannot bind rvalue '(short unsigned int)((long long int*)(& a))' to 'short unsigned int&'
/usr/include/c++/14/istream:181:7: note: candidate: 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(int&) [with _CharT = char; _Traits = std::char_traits<char>]' (near match)
  181 |       operator>>(int& __n);
      |       ^~~~~~~~
/usr/include/c++/14/istream:181:7: note:   conversion of argument 1 would be ill-formed:
a.cc:98:10: error: invalid conversion from 'long long int*' to 'int' [-fpermissive]
   98 |     cin>>a;
      |          ^
      |          |
      |          long long int*
a.cc:98:10: error: cannot bind rvalue '(int)((long long int*)(& a))' to 'int&'
/usr/include/c++/14/istream:184:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  184 |       operator>>(unsigned int& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:184:7: note:   conversion of argument 1 would be ill-formed:
a.cc:98:10: error: invalid conversion from 'long long int*' to 'unsigned int' [-fpermissive]
   98 |     cin>>a;
      |          ^
      |          |
      |          long long int*
a.cc:98:10: error: cannot bind rvalue '(unsigned int)((long long int*)(& a))' to 'unsigned int&'
/usr/include/c++/14/istream:188:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  188 |       operator>>(long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:188:7: note:   conversion of argument 1 would be ill-formed:
a.cc:98:10: error: invalid conversion from 'long long int*' to 'long int' [-fpermissive]
   98 |     cin>>a;
      |          ^
      |          |
      |          long long int*
a.cc:98:10: error: cannot bind rvalue '(long int)((long long int*)(& a))' to 'long int&'
/usr/include/c++/14/istream:192:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  192 |       operator>>(unsigned long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:192:7: note:   conversion of argument 1 would be ill-formed:
a.cc:98:10: error: invalid conversion from 'long long int*' to 'long unsigned int' [-fpermissive]
   98 |     cin>>a;
      |          ^
      |          |
      |          long long int*
a.cc:98:10: error: cannot bind rvalue '(long unsigned int)((long long int*)(& a))' to 'long unsigned int&'
/usr/include/c++/14/istream:199:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long long int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  199 |       operator>>(long long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:199:7: note:   conversion of argument 1 would be ill-formed:
a.cc:98:10: error: invalid conversion from 'long long int*' to 'long long int' [-fpermissive]
   98 |     cin>>a;
      |          ^
      |          |
      |          long long int*
a.cc:98:10: error: cannot bind rvalue '(long long int)((long long int*)(& a))' to 'long long int&'
/usr/include/c++/14/istream:203:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long long unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  203 |       operator>>(unsigned long long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:203:7: note:   conversion of argument 1 would be ill-formed:
a.cc:98:10: error: invalid conversion from 'long long int*' to 'long long unsigned int' [-fpermissive]
   98 |     cin>>a;
      |          ^
      |          |
      |          long long int*
a.cc:98:10: error: cannot bind rvalue '(long long unsigned int)((long long int*)(& a))' to 'long long unsigned int&'
/usr/include/c++/14/istream:328:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(void*&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  328 |       operator>>(void*& __p)
      |       ^~~~~~~~
/usr/include/c++/14/istream:328:7: note:   conversion of argument 1 would be ill-formed:
a.cc:98:10: error: cannot bind non-const lvalue reference of type 'void*&' to an rvalue of type 'void*'
   98 |     cin>>a;
      |          ^
/usr/include/c++/14/istream:219:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(float&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]'
  219 |       operator>>(float& __f)
      |       ^~~~~~~~
/usr/include/c++/14/istream:219:25: note:   no known conversion for argument 1 from 'long long int [1000005]' to 'float&'
  219 |       operator>>(float& __f)
      |                  ~~~~~~~^~~
/usr/include/c++/14/istream:223:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(double&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]'
  223 |       operator>>(double& __f)
      |       ^~~~~~~~
/usr/include/c++/14/istream:223:26: note:   no known conversion for argument 1 from 'long long int [1000005]' to 'double&'
  223 |       operator>>(double& __f)
      |                  ~~~~~~~~^~~
/usr/include/c++/14/istream:227:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long double&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]'
  227 |       operator>>(long double& __f)
      |       ^~~~~~~~
/usr/include/c++/14/istream:227:31: note:   no known conversion for argument 1 from 'long long int [1000005]' to 'long double&'
  227 |       operator>>(long double& __f)
      |                  ~~~~~~~~~~~~~^~~
/usr/include/c++/14/istream:122:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(__istream_type& (*)(__istream_type&)) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]'
  122 |       operator>>(__istream_type& (*__pf)(__istream_type&))
      |       ^~~~~~~~
/usr/include/c++/14/istream:122:36: note:   no known conversion for argument 1 from 'long long int [1000005]' to 'std::basic_istream<char>::__istream_type& (*)(std::basic_istream<char>::