#include <stdio.h>
 
int main() {
    int n, k;
    scanf("%d %d", &n, &k);
 
    char password[n + 1];
    password[n] = '\0';
 
    int i;
    for (i = 0; i < n - k; i++) {
        password[i] = 'A';
    }
 
    char ch = 'A';
    for (; i < n; i++) {
        password[i] = ch++;
    }
 
    printf("%s\n", password);
 
    return 0;
}