x.cpp

#pragma GCC optimize("Ofast")
#pragma GCC optimize ("unroll-loops")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")

#include <iostream>
#include <string>
#include <algorithm>
#include <set>
#include <map>
#include <vector>

using namespace std;
int cases;
int n;
unsigned long long ans;

int main() {
    cin.tie(0);
    ios_base::sync_with_stdio(false);
    cin >> cases;
    int R, C;
    for (int _case = 1; _case <= cases; _case++) {
        cin >> R >> C;
        bool reverted = R > C;
        if (reverted) {
            int t = R;
            R = C;
            C = t;
        }
        bool good;
        if (R == 2) {
            good = C > 4;
        } else {
            good = C > 3;
        }

        if (good) {
            cout << "Case #" << _case << ": POSSIBLE\n";
            int i = 1;
            int j = 1;
            int cnt = C*R;
            bool right = true;
            int jump = R == 2 ? 3 : 2;
            int startj = 1;
            while (cnt > 0) {
                if (reverted){
                    cout << j << " " << i << "\n";
                } else {
                    cout << i << " " << j << "\n";
                }
                i++;
                if (i > R) {
                    i = 1;
                    startj++;
                    j = startj;
                    right = true;
                } else{
                    if (right) {
                        j += jump;
                        if (j > C) {
                            j -= C;
                        }
                    } else {
                        j -= jump;
                        if (j < 1) {
                            j += C;
                        }
                    }
                    right = !right;
                }
                cnt--;
            }
        } else {
            cout << "Case #" << _case << ": IMPOSSIBLE\n";
        }
    }
    return 0;
}