Language: C++

#include <bits/stdc++.h>
using namespace std;
#define rep(i, n)  for(long long i=0;i<(long long)(n);i++)
#define REP(i,k,n) for(long long i=k;i<(long long)(n);i++)
#define all(a) a.begin(),a.end()
#define pb push_back
#define eb emplace_back
#define lb(v,k) (lower_bound(all(v),k)-v.begin())
#define ub(v,k) (upper_bound(all(v),k)-v.begin())
#define fi first
#define se second
#define pi M_PI
typedef long long ll;
typedef pair<ll,ll> P;
typedef tuple<ll,ll,ll> PP;
typedef multiset<ll> S;
typedef priority_queue<ll> PQ;
typedef priority_queue<P,vector<P>,greater<P>> SPQ;
using vi=vector<ll>;
using vvi=vector<vi>;
using vvvi=vector<vvi>;
using vp=vector<P>;
using vvp=vector<vp>;
using vb=vector<bool>;
const ll inf=1001001001001001;
const int INF=1001001001;
const int mod=1000000007;
template<class T> bool chmin(T&a,T b){if(a>b){a=b;return true;}return false;}
template<class T> bool chmax(T&a,T b){if(a<b){a=b;return true;}return false;}
template<class T> void out(T a){cout<<a<<'\n';}
template<class T> void outp(T a){cout<<'('<<a.fi<<','<<a.se<<')'<<'\n';}
template<class T> void outvp(T v){rep(i,v.size())outp(v[i]);}
template<class T> void outv(T v){rep(i,v.size()){if(i)cout<<' ';cout<<v[i];}cout<<'\n';}
template<class T> void outvv(T v){rep(i,v.size()){rep(j,v[i].size()){if(j)cout<<' ';cout<<v[i][j];}cout<<'\n';}}
ll gcd(ll a,ll b){if(b==0)return a;return gcd(b,a%b);}
ll modpow(ll a,ll b){a%=mod;if(b==0)return 1;if(b&1)return a*modpow(a,b-1)%mod;ll k=modpow(a,b/2);return k*k%mod;}

int main(){
    ll h,w;cin>>h>>w;#include <bits/stdc++.h>
using namespace std;
#define rep(i, n)  for(long long i=0;i<(long long)(n);i++)
#define REP(i,k,n) for(long long i=k;i<(long long)(n);i++)
#define all(a) a.begin(),a.end()
#define pb push_back
#define eb emplace_back
#define lb(v,k) (lower_bound(all(v),k)-v.begin())
#define ub(v,k) (upper_bound(all(v),k)-v.begin())
#define fi first
#define se second
#define pi M_PI
typedef long long ll;
typedef pair<ll,ll> P;
typedef tuple<ll,ll,ll> PP;
typedef multiset<ll> S;
typedef priority_queue<ll> PQ;
typedef priority_queue<P,vector<P>,greater<P>> SPQ;
using vi=vector<ll>;
using vvi=vector<vi>;
using vvvi=vector<vvi>;
using vp=vector<P>;
using vvp=vector<vp>;
using vb=vector<bool>;
const ll inf=1001001001001001;
const int INF=1001001001;
const int mod=1000000007;
template<class T> bool chmin(T&a,T b){if(a>b){a=b;return true;}return false;}
template<class T> bool chmax(T&a,T b){if(a<b){a=b;return true;}return false;}
template<class T> void out(T a){cout<<a<<'\n';}
template<class T> void outp(T a){cout<<'('<<a.fi<<','<<a.se<<')'<<'\n';}
template<class T> void outvp(T v){rep(i,v.size())outp(v[i]);}
template<class T> void outv(T v){rep(i,v.size()){if(i)cout<<' ';cout<<v[i];}cout<<'\n';}
template<class T> void outvv(T v){rep(i,v.size()){rep(j,v[i].size()){if(j)cout<<' ';cout<<v[i][j];}cout<<'\n';}}
ll gcd(ll a,ll b){if(b==0)return a;return gcd(b,a%b);}
ll modpow(ll a,ll b){a%=mod;if(b==0)return 1;if(b&1)return a*modpow(a,b-1)%mod;ll k=modpow(a,b/2);return k*k%mod;}

int main(){
    ll h,w;cin>>h>>w;
    ll ans;
    if(h%2==0){
        ans=h/2*w;
    }
    else if(w%2==0)ans=w/2*h;
    else ans=w*h/2+1;
    out(ans);
}
    ll ans;
    if(h%2==0){
        ans=h/2*w;
    }
    else if(w%2==0)ans=w/2*h;
    else 
    ll ans=((h+1)/2)*((w+1)/2)+((h/2)*(w/2));
    out(ans);
}

Compiler output:
a.cc:39:22: error: stray '#' in program
   39 |     ll h,w;cin>>h>>w;#include <bits/stdc++.h>
      |                      ^
a.cc: In function 'int main()':
a.cc:39:23: error: 'include' was not declared in this scope
   39 |     ll h,w;cin>>h>>w;#include <bits/stdc++.h>
      |                       ^~~~~~~
a.cc:39:32: error: 'bits' was not declared in this scope
   39 |     ll h,w;cin>>h>>w;#include <bits/stdc++.h>
      |                                ^~~~
a.cc:39:37: error: 'stdc' was not declared in this scope; did you mean 'std'?
   39 |     ll h,w;cin>>h>>w;#include <bits/stdc++.h>
      |                                     ^~~~
      |                                     std
a.cc:40:1: error: expected primary-expression before 'using'
   40 | using namespace std;
      | ^~~~~
a.cc:66:1: error: a template declaration cannot appear at block scope
   66 | template<class T> bool chmin(T&a,T b){if(a>b){a=b;return true;}return false;}
      | ^~~~~~~~
a.cc:68:1: error: a template declaration cannot appear at block scope
   68 | template<class T> void out(T a){cout<<a<<'\n';}
      | ^~~~~~~~
a.cc:70:1: error: a template declaration cannot appear at block scope
   70 | template<class T> void outvp(T v){rep(i,v.size())outp(v[i]);}
      | ^~~~~~~~
a.cc:72:1: error: a template declaration cannot appear at block scope
   72 | template<class T> void outvv(T v){rep(i,v.size()){rep(j,v[i].size()){if(j)cout<<' ';cout<<v[i][j];}cout<<'\n';}}
      | ^~~~~~~~
a.cc:74:21: error: a function-definition is not allowed here before '{' token
   74 | ll modpow(ll a,ll b){a%=mod;if(b==0)return 1;if(b&1)return a*modpow(a,b-1)%mod;ll k=modpow(a,b/2);return k*k%mod;}
      |                     ^
a.cc:76:9: warning: empty parentheses were disambiguated as a function declaration [-Wvexing-parse]
   76 | int main(){
      |         ^~
a.cc:76:9: note: remove parentheses to default-initialize a variable
   76 | int main(){
      |         ^~
      |         --
a.cc:76:9: note: or replace parentheses with braces to value-initialize a variable
a.cc:76:11: error: a function-definition is not allowed here before '{' token
   76 | int main(){
      |           ^