1010 - Knights in Chessboard

#include <iostream>
#include <cstdio>
using namespace std;

int main()
{
    int t_c, t = 1;
    cin >> t_c;
    int m, n;
    while(t_c--)
    {
        int res;
        cin >> m >> n;
        if(m > n)
        {
            m ^= n;
            n ^= m;
            m ^= n;
        }
        //cout << m << ' ' << n;
        if(m == 1) res = n;
        else if(m == 2)
        {
            if((m * n) == 4) res = 4;
            else
            {
                if(n & 1) res = n+1;
                else
                {
                    if(n % 4 == 0) res = n;
                    else res = n+2;
                }
            }
        }
        else
        {
            int temp = m * n;
            if(temp & 1) res = (temp / 2) + 1;
            else res = temp / 2;
        }
        printf("Case %d: %d\n", t++ , res);
    }

    return 0;
}