L-Trominos

#include <iostream>
#include <string>

using namespace std;

char res[105][105];

void printres(int n, int m) {
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < m; ++j) {
            cout << res[i][j];
        }
        cout << "\n";
    }
}

void printresinv(int n, int m) {
    for (int j = 0; j < n; ++j) {
        for (int i = 0; i < m; ++i) {
            cout << res[i][j];
        }
        cout << "\n";
    }
}

void onlyhoriz(int n, int m) {
    string t[4] = {"AAB", "ABB", "CCD", "CDD"};
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < m/3; ++j) {
            string s = t[i%4];
            for (int k = 0; k < 3; ++k) {
                res[i][3*j+k] = s[k];
            }
        }
    }
}

void doublevert(int n, int m) {
    string t[4] = {"AAB", "ABB", "CCD", "CDD"};
    string v[3] = {"EE", "EF", "FF"};
    string v2[3] = {"GG", "GH", "HH"};
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < m/3 - 1; ++j) {
            string s = t[i%4];
            for (int k = 0; k < 3; ++k) {
                res[i][3*j+k] = s[k];
            }
        }
        string s = v[i%3];
        res[i][3*(m/3-1)] = s[0];
        res[i][3*(m/3-1)+1] = s[1];
        
        string s2 = v2[i%3];
        res[i][3*(m/3-1)+2] = s2[0];
        res[i][3*(m/3-1)+3] = s2[1];
    }
}

void singlevert(int n, int m) {
    string t[4] = {"AAB", "ABB", "CCD", "CDD"};
    string v[3] = {"EE", "EF", "FF"};
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < m/3; ++j) {
            string s = t[i%4];
            for (int k = 0; k < 3; ++k) {
                res[i][3*j+k] = s[k];
            }
        }
        string s = v[i%3];
        res[i][3*(m/3)] = s[0];
        res[i][3*(m/3)+1] = s[1];
    }
}

bool solve(int y, int x) {
    if (y == 1 || x == 1) return false;
    
    if (x%3 == 0) {
        if (y%2 == 0) {
            onlyhoriz(y, x);
        }
        else {
            return false;
        }
    }
    else if (x%3 == 1) {
        if (y%6 == 0) {
            doublevert(y, x);
        }
        else {
            return false;
        }
    }
    else {
        if (y%6 == 0) {
            singlevert(y, x);
        }
        else {
            return false;
        }
    }
    return true;
}


int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    int n, m;
    cin >> n >> m;
    if (solve(n, m)) printres(n, m);
    else if (solve(m, n)) printresinv(n, m);
    else cout << "IMPOSSIBLE\n";
    return 0;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED

Test 15

Verdict: ACCEPTED

Test 16

Verdict: ACCEPTED

Test 17

Verdict: ACCEPTED

Test 18

Verdict: ACCEPTED

Test 19

Verdict: ACCEPTED

Test 20

Verdict: ACCEPTED

Test 21

Verdict: ACCEPTED

Test 22

Verdict: ACCEPTED

Test 23

Verdict: ACCEPTED

Test 24

Verdict: ACCEPTED

Test 25

Verdict: ACCEPTED

Test 26

Verdict: ACCEPTED

Test 27

Verdict: ACCEPTED

Test 28

Verdict: ACCEPTED

Test 29

Verdict: ACCEPTED

Test 30

Verdict: ACCEPTED

Test 31

Verdict: ACCEPTED

Test 32

Verdict: ACCEPTED

Test 33

Verdict: ACCEPTED

Test 34

Verdict: ACCEPTED

Test 35

Verdict: ACCEPTED

Test 36

Verdict: ACCEPTED

Test 37

Verdict: ACCEPTED

Test 38

Verdict: WRONG ANSWER

Test 39

Verdict: ACCEPTED

Test 40

Verdict: ACCEPTED

Test 41

Verdict: ACCEPTED

Test 42

Verdict: ACCEPTED

Test 43

Verdict: ACCEPTED

Test 44

Verdict: ACCEPTED

Test 45

Verdict: ACCEPTED

Test 46

Verdict: ACCEPTED

Test 47

Verdict: ACCEPTED

Test 48

Verdict: ACCEPTED

Test 49

Verdict: ACCEPTED

Test 50

Verdict: ACCEPTED

Test 51

Verdict: WRONG ANSWER

Test 52

Verdict: ACCEPTED

Test 53

Verdict: ACCEPTED

Test 54

Verdict: ACCEPTED

Test 55

Verdict: ACCEPTED

Test 56

Verdict: ACCEPTED

Test 57

Verdict: ACCEPTED

Test 58

Verdict: ACCEPTED

Test 59

Verdict: WRONG ANSWER

Test 60

Verdict: ACCEPTED

Test 61

Verdict: WRONG ANSWER

Test 62

Verdict: ACCEPTED

Test 63

Verdict: WRONG ANSWER

Test 64

Verdict: ACCEPTED

Test 65

Verdict: ACCEPTED

Test 66

Verdict: ACCEPTED

Test 67

Verdict: ACCEPTED

Test 68

Verdict: ACCEPTED

Test 69

Verdict: ACCEPTED

Test 70

Verdict: ACCEPTED

Test 71

Verdict: ACCEPTED

Test 72

Verdict: WRONG ANSWER

Test 73

Verdict: ACCEPTED

Test 74

Verdict: ACCEPTED

Test 75

Verdict: WRONG ANSWER

Test 76

Verdict: WRONG ANSWER

Test 77

Verdict: ACCEPTED

Test 78

Verdict: WRONG ANSWER

Test 79

Verdict: ACCEPTED

Test 80

Verdict: WRONG ANSWER

Test 81

Verdict: ACCEPTED

Test 82

Verdict: ACCEPTED

Test 83

Verdict: ACCEPTED

Test 84

Verdict: ACCEPTED

Test 85

Verdict: ACCEPTED

Test 86

Verdict: ACCEPTED

Test 87

Verdict: ACCEPTED

Test 88

Verdict: ACCEPTED

Test 89

Verdict: ACCEPTED

Test 90

Verdict: ACCEPTED

Test 91

Verdict: ACCEPTED