Language: C++

#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<algorithm>
#define pb push_back
#define all(c) c.begin(),c.end()
#define uni(c) c.erase(unique(all(c)),c.end())
using namespace std;
typedef __int64 ll;
int main(){
	string s;
	while(cin>>s){
		map<char,ll> m;
		for(ll i=0;i<s.size();i++){
			m[s[i]]++;
		}
		
		ll odd=0,even=0;
		map<char,ll>::iterator ite=m.begin();
		vector<ll> v;
		for(ite=m.begin();ite!=m.end();ite++){
			if(ite->second%2==1){
				odd++;
				if(ite->second>=3)
				v.pb((ite->second-1)/2);
			}else{
				even++;
				v.pb((ite->second)/2);
			}
		}
		if(odd>1){
			cout<<0<<endl;
			continue;
		}
		int ans=1;
		for(int i=1;i<=s.size()/2;i++){
			//cout<<ans<<endl;
			if(find(all(v),i)!=v.end()){
				v.erase(find(all(v),i));
			}else
			ans*=i;
		}
		cout<<ans<<endl;
	}
	return 0;
}

Compiler output:
a.cc:11:9: error: '__int64' does not name a type; did you mean '__int64_t'?
   11 | typedef __int64 ll;
      |         ^~~~~~~
      |         __int64_t
a.cc: In function 'int main()':
a.cc:15:26: error: 'll' was not declared in this scope; did you mean 'all'?
   15 |                 map<char,ll> m;
      |                          ^~
      |                          all
a.cc:15:28: error: template argument 2 is invalid
   15 |                 map<char,ll> m;
      |                            ^
a.cc:15:28: error: template argument 4 is invalid
a.cc:16:23: error: expected ';' before 'i'
   16 |                 for(ll i=0;i<s.size();i++){
      |                       ^~
      |                       ;
a.cc:16:28: error: 'i' was not declared in this scope
   16 |                 for(ll i=0;i<s.size();i++){
      |                            ^
a.cc:20:19: error: expected ';' before 'odd'
   20 |                 ll odd=0,even=0;
      |                   ^~~~
      |                   ;
a.cc:21:28: error: template argument 4 is invalid
   21 |                 map<char,ll>::iterator ite=m.begin();
      |                            ^
a.cc:21:40: error: expected initializer before 'ite'
   21 |                 map<char,ll>::iterator ite=m.begin();
      |                                        ^~~
a.cc:22:26: error: template argument 2 is invalid
   22 |                 vector<ll> v;
      |                          ^
a.cc:23:21: error: 'ite' was not declared in this scope
   23 |                 for(ite=m.begin();ite!=m.end();ite++){
      |                     ^~~
a.cc:23:27: error: request for member 'begin' in 'm', which is of non-class type 'int'
   23 |                 for(ite=m.begin();ite!=m.end();ite++){
      |                           ^~~~~
a.cc:23:42: error: request for member 'end' in 'm', which is of non-class type 'int'
   23 |                 for(ite=m.begin();ite!=m.end();ite++){
      |                                          ^~~
a.cc:25:33: error: 'odd' was not declared in this scope
   25 |                                 odd++;
      |                                 ^~~
a.cc:7:12: error: request for member 'push_back' in 'v', which is of non-class type 'int'
    7 | #define pb push_back
      |            ^~~~~~~~~
a.cc:27:35: note: in expansion of macro 'pb'
   27 |                                 v.pb((ite->second-1)/2);
      |                                   ^~
a.cc:29:33: error: 'even' was not declared in this scope
   29 |                                 even++;
      |                                 ^~~~
a.cc:7:12: error: request for member 'push_back' in 'v', which is of non-class type 'int'
    7 | #define pb push_back
      |            ^~~~~~~~~
a.cc:30:35: note: in expansion of macro 'pb'
   30 |                                 v.pb((ite->second)/2);
      |                                   ^~
a.cc:33:20: error: 'odd' was not declared in this scope
   33 |                 if(odd>1){
      |                    ^~~
a.cc:8:18: error: request for member 'begin' in 'v', which is of non-class type 'int'
    8 | #define all(c) c.begin(),c.end()
      |                  ^~~~~
a.cc:40:33: note: in expansion of macro 'all'
   40 |                         if(find(all(v),i)!=v.end()){
      |                                 ^~~
a.cc:8:28: error: request for member 'end' in 'v', which is of non-class type 'int'
    8 | #define all(c) c.begin(),c.end()
      |                            ^~~
a.cc:40:33: note: in expansion of macro 'all'
   40 |                         if(find(all(v),i)!=v.end()){
      |                                 ^~~
a.cc:40:46: error: request for member 'end' in 'v', which is of non-class type 'int'
   40 |                         if(find(all(v),i)!=v.end()){
      |                                              ^~~
a.cc:41:35: error: request for member 'erase' in 'v', which is of non-class type 'int'
   41 |                                 v.erase(find(all(v),i));
      |                                   ^~~~~
a.cc:8:18: error: request for member 'begin' in 'v', which is of non-class type 'int'
    8 | #define all(c) c.begin(),c.end()
      |                  ^~~~~
a.cc:41:46: note: in expansion of macro 'all'
   41 |                                 v.erase(find(all(v),i));
      |                                              ^~~
a.cc:8:28: error: request for member 'end' in 'v', which is of non-class type 'int'
    8 | #define all(c) c.begin(),c.end()
      |                            ^~~
a.cc:41:46: note: in expansion of macro 'all'
   41 |                                 v.erase(find(all(v),i));
      |                                              ^~~