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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3. int main() {
  4. ios::sync_with_stdio(false);
  5. cin.tie(0), cout.tie(0);
  6. long long n,m,sum=0; cin >> n >> m;
  7. for(int i=1,cur=1;i<=m;i++) {
  8. if(i%2!=0) sum+=cur;
  9. else sum+=n-cur+1, cur++;
  10. }
  11. cout << sum;
  12. return 0;
  13. }
Success #stdin #stdout 0.01s 5288KB
stdin
6 3
stdout
9