#include <iostream>
#include <vector>
using namespace std;
using chr_t = char;
using coord_t = size_t;
struct coord {
coord_t x, y; };
const chr_t content[] = {
"ABCDEFGHIJKLMNOPQRSTUVWXYZ" };
const chr_t delim[] = " ";
const size_t CONTENT_SIZE = sizeof(content) / sizeof(chr_t) - 1;
inline bool next_pos(const size_t M, const size_t N, const vector<vector<chr_t>>& a, coord& c) {
static unsigned direction = 0;
for (unsigned i = 0; i < 4; ++i) {
switch (direction) {
case 0:
if (c.y < N - 1 && a[c.x][c.y + 1] == 0) {
++c.y; return true; }
else {
direction = (direction + 1) % 4; }
continue;
case 1:
if (c.x < M - 1 && a[c.x + 1][c.y] == 0) {
++c.x; return true; }
else {
direction = (direction + 1) % 4; }
continue;
case 2:
if (c.y > 0 && a[c.x][c.y - 1] == 0) {
--c.y; return true; }
else {
direction = (direction + 1) % 4; }
continue;
case 3:
if (c.x > 0 && a[c.x - 1][c.y] == 0) {
--c.x; return true; }
else {
direction = (direction + 1) % 4; }
continue;
}
}
return false;
}
int main() {
size_t M, N;
for (;;) {
cout << "Input M, N:" << endl;
cin >> M >> N;
if (M == 0 && N == 0) return 0;
vector<chr_t> t(N, 0);
vector<vector<chr_t>> a(M, t);
coord c = {
0, 0 };
coord_t& x = c.x, & y = c.y;
size_t i = 0;
do {
a[x][y] = content[i];
i = (i + 1) % CONTENT_SIZE;
} while (next_pos(M, N, a, c) == true);
cout << endl;
for (vector<vector<chr_t>>::const_iterator i = a.cbegin(); i != a.cend(); ++i) {
for (vector<chr_t>::const_iterator j = i->cbegin(); j != i->cend(); ++j) {
cout << *j << delim;
}
cout << endl;
}
cout << endl;
}
}
