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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3. #define nl '\n'
  4. typedef long long ll;
  5. #define int long long
  6.  
  7. void File() {
  8. #ifndef ONLINE_JUDGE
  9.     freopen("input.txt", "r", stdin);
  10.     freopen("output.txt", "w", stdout);
  11. #endif
  12.     ios::sync_with_stdio(false), cin.tie(nullptr), cout.tie(nullptr);
  13. }
  14.  
  15. void sol() {
  16.     int a,b;
  17.     cin >> a >> b;
  18.     if(!(a&1) and !(b&1)) {
  19.         cout << a*(b/2)+2 << '\n';
  20.     }else if(!(a&1) and b&1) {
  21.         cout << -1 << '\n';
  22.     }else if(a&1 and !(b&1)) {
  23.         if((b/2)&1) {
  24.             cout << -1 <<'\n';
  25.         }else {
  26.             cout << a*(b/2)+2 << '\n';
  27.         }
  28.     }else {
  29.         cout << a*b+1 << '\n';
  30.     }
  31. }
  32. signed main() {
  33.     File();
  34.     int T{1};
  35.     cin >> T;
  36.     while (T--) {
  37.         sol();
  38.     }
  39. }
  40.  
Success #stdin #stdout 0s 5300KB
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Standard input is empty
stdout
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2
https://ideone.com/2uXuxP
language:
C++14 (gcc 8.3)
created:
10 days ago
visibility:
public

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