https://old.ynoip.cn/p/90001

#include <cstdio>
using namespace std;

int main(void) {
	int n;
	scanf("%d", &n);
	for (int i = 0; i < n; i++) {
		for (int u = 0; u < n; u++) {
			printf("%c", 'A' + ((i + u) % 26));
		}
		printf("\n");
	}
	return 0;
}