Language: C++

using namespace std;
const int N = 200005;
int w,h,k,n;
map <pair<int,int>,int> M,Map;
pair<int,int> a[N];
int main(){
	scanf("%d%d%d",&w,&h,&k);
	scanf("%d",&n);
	Map.clear();
	M.clear();
	for (int i = 1; i <= n; i++){
		scanf("%d%d",&a[i].first,&a[i].second);
		Map[a[i]] = 1;
	}
	k -= (w + 1) / 2;
	int s = 0;
	sort(a + 1, a + n + 1);
	for (int i = 1; i <= n; i++)
		if (a[i].first % 2 == 1 && a[i].second % 2 == 0){
			if (M[make_pair(a[i].first,a[i].second - 1)]) continue;
			if (a[i].first < w)
				if ((Map[make_pair(a[i].first + 1,a[i].second)] == 0) && (M[make_pair(a[i].first + 2,a[i].second - 1)] == 0)){
					M[make_pair(a[i].first + 2,a[i].second - 1)] = 1;
					continue;
				}
			if (a[i].first > 1)
				if ((Map[make_pair(a[i].first - 1,a[i].second)] == 0) && (M[make_pair(a[i].first - 2,a[i].second - 1)] == 0)){
					M[make_pair(a[i].first - 2,a[i].second - 1)] = 1;
					continue;
				}
			s++;
//			printf("!%d\n",i);
		}
	int ss = ((w + 1) / 2) * ((h + 1) / 2);;
	ss -= s;
	ss -= (w + 1) / 2;
//	printf("%d %d\n",s,ss);
	if (k > s){
		k -= s;
		s = 0;
		ss -= k;
	} s -= k;
	printf("%d\n",s * 2 + ss);
}

Compiler output:
a.cc:4:1: error: 'map' does not name a type
    4 | map <pair<int,int>,int> M,Map;
      | ^~~
a.cc:5:1: error: 'pair' does not name a type
    5 | pair<int,int> a[N];
      | ^~~~
a.cc: In function 'int main()':
a.cc:7:9: error: 'scanf' was not declared in this scope
    7 |         scanf("%d%d%d",&w,&h,&k);
      |         ^~~~~
a.cc:9:9: error: 'Map' was not declared in this scope
    9 |         Map.clear();
      |         ^~~
a.cc:10:9: error: 'M' was not declared in this scope
   10 |         M.clear();
      |         ^
a.cc:12:31: error: 'a' was not declared in this scope
   12 |                 scanf("%d%d",&a[i].first,&a[i].second);
      |                               ^
a.cc:17:14: error: 'a' was not declared in this scope
   17 |         sort(a + 1, a + n + 1);
      |              ^
a.cc:17:9: error: 'sort' was not declared in this scope; did you mean 'short'?
   17 |         sort(a + 1, a + n + 1);
      |         ^~~~
      |         short
a.cc:20:31: error: 'make_pair' was not declared in this scope
   20 |                         if (M[make_pair(a[i].first,a[i].second - 1)]) continue;
      |                               ^~~~~~~~~
a.cc:1:1: note: 'std::make_pair' is defined in header '<utility>'; this is probably fixable by adding '#include <utility>'
  +++ |+#include <utility>
    1 | using namespace std;
a.cc:22:42: error: 'make_pair' was not declared in this scope
   22 |                                 if ((Map[make_pair(a[i].first + 1,a[i].second)] == 0) && (M[make_pair(a[i].first + 2,a[i].second - 1)] == 0)){
      |                                          ^~~~~~~~~
a.cc:22:42: note: 'std::make_pair' is defined in header '<utility>'; this is probably fixable by adding '#include <utility>'
a.cc:27:42: error: 'make_pair' was not declared in this scope
   27 |                                 if ((Map[make_pair(a[i].first - 1,a[i].second)] == 0) && (M[make_pair(a[i].first - 2,a[i].second - 1)] == 0)){
      |                                          ^~~~~~~~~
a.cc:27:42: note: 'std::make_pair' is defined in header '<utility>'; this is probably fixable by adding '#include <utility>'
a.cc:43:9: error: 'printf' was not declared in this scope
   43 |         printf("%d\n",s * 2 + ss);
      |         ^~~~~~
a.cc:1:1: note: 'printf' is defined in header '<cstdio>'; this is probably fixable by adding '#include <cstdio>'
  +++ |+#include <cstdio>
    1 | using namespace std;