Language: C++

#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
#define long long unsigned long long int
int main(){
    long long int n;
    cin>>n;
    long long int ans=0;
    
    if(n%2==1){
        cout<<0<<endl;
    }
    else{
    	long long int f=10;
        for(int i=0;i<19;i++){
            ans=ans+(n/f);
            f=f*10;
        }
        cout<<ans<<endl;
    }


    return 0;
}





Compiler output:
a.cc: In function 'int main()':
a.cc:5:33: error: 'long long long' is too long for GCC
    5 | #define long long unsigned long long int
      |                                 ^~~~
a.cc:7:5: note: in expansion of macro 'long'
    7 |     long long int n;
      |     ^~~~
a.cc:5:14: error: 'long long long' is too long for GCC
    5 | #define long long unsigned long long int
      |              ^~~~
a.cc:7:10: note: in expansion of macro 'long'
    7 |     long long int n;
      |          ^~~~
a.cc:5:19: error: duplicate 'unsigned'
    5 | #define long long unsigned long long int
      |                   ^~~~~~~~
a.cc:7:10: note: in expansion of macro 'long'
    7 |     long long int n;
      |          ^~~~
a.cc:5:28: error: 'long long long' is too long for GCC
    5 | #define long long unsigned long long int
      |                            ^~~~
a.cc:7:10: note: in expansion of macro 'long'
    7 |     long long int n;
      |          ^~~~
a.cc:5:33: error: 'long long long' is too long for GCC
    5 | #define long long unsigned long long int
      |                                 ^~~~
a.cc:7:10: note: in expansion of macro 'long'
    7 |     long long int n;
      |          ^~~~
a.cc:5:38: error: two or more data types in declaration of 'n'
    5 | #define long long unsigned long long int
      |                                      ^~~
a.cc:7:5: note: in expansion of macro 'long'
    7 |     long long int n;
      |     ^~~~
a.cc:8:10: error: 'n' was not declared in this scope
    8 |     cin>>n;
      |          ^
a.cc:5:33: error: 'long long long' is too long for GCC
    5 | #define long long unsigned long long int
      |                                 ^~~~
a.cc:9:5: note: in expansion of macro 'long'
    9 |     long long int ans=0;
      |     ^~~~
a.cc:5:14: error: 'long long long' is too long for GCC
    5 | #define long long unsigned long long int
      |              ^~~~
a.cc:9:10: note: in expansion of macro 'long'
    9 |     long long int ans=0;
      |          ^~~~
a.cc:5:19: error: duplicate 'unsigned'
    5 | #define long long unsigned long long int
      |                   ^~~~~~~~
a.cc:9:10: note: in expansion of macro 'long'
    9 |     long long int ans=0;
      |          ^~~~
a.cc:5:28: error: 'long long long' is too long for GCC
    5 | #define long long unsigned long long int
      |                            ^~~~
a.cc:9:10: note: in expansion of macro 'long'
    9 |     long long int ans=0;
      |          ^~~~
a.cc:5:33: error: 'long long long' is too long for GCC
    5 | #define long long unsigned long long int
      |                                 ^~~~
a.cc:9:10: note: in expansion of macro 'long'
    9 |     long long int ans=0;
      |          ^~~~
a.cc:5:38: error: two or more data types in declaration of 'ans'
    5 | #define long long unsigned long long int
      |                                      ^~~
a.cc:9:5: note: in expansion of macro 'long'
    9 |     long long int ans=0;
      |     ^~~~
a.cc:5:33: error: 'long long long' is too long for GCC
    5 | #define long long unsigned long long int
      |                                 ^~~~
a.cc:15:9: note: in expansion of macro 'long'
   15 |         long long int f=10;
      |         ^~~~
a.cc:5:14: error: 'long long long' is too long for GCC
    5 | #define long long unsigned long long int
      |              ^~~~
a.cc:15:14: note: in expansion of macro 'long'
   15 |         long long int f=10;
      |              ^~~~
a.cc:5:19: error: duplicate 'unsigned'
    5 | #define long long unsigned long long int
      |                   ^~~~~~~~
a.cc:15:14: note: in expansion of macro 'long'
   15 |         long long int f=10;
      |              ^~~~
a.cc:5:28: error: 'long long long' is too long for GCC
    5 | #define long long unsigned long long int
      |                            ^~~~
a.cc:15:14: note: in expansion of macro 'long'
   15 |         long long int f=10;
      |              ^~~~
a.cc:5:33: error: 'long long long' is too long for GCC
    5 | #define long long unsigned long long int
      |                                 ^~~~
a.cc:15:14: note: in expansion of macro 'long'
   15 |         long long int f=10;
      |              ^~~~
a.cc:5:38: error: two or more data types in declaration of 'f'
    5 | #define long long unsigned long long int
      |                                      ^~~
a.cc:15:9: note: in expansion of macro 'long'
   15 |         long long int f=10;
      |         ^~~~
a.cc:17:13: error: 'ans' was not declared in this scope; did you mean 'abs'?
   17 |             ans=ans+(n/f);
      |             ^~~
      |             abs
a.cc:17:24: error: 'f' was not declared in this scope
   17 |             ans=ans+(n/f);
      |                        ^
a.cc:20:15: error: 'ans' was not declared in this scope; did you mean 'abs'?
   20 |         cout<<ans<<endl;
      |               ^~~
      |               abs