import std;

void main() {
    int n, d; scan(n, d);

    if (d > n) {
        int b = d - n;
        int a = n - b;
        writeln(repeat('A', a), repeat('B', b));
    }
    else {
        writeln(repeat('A', d), repeat('C', n - d));
    }
}

void scan(T...)(ref T a) {
    string[] ss = readln.split;
    foreach (i, t; T) a[i] = ss[i].to!t;
}
T read(T)() { return readln.chomp.to!T; }
T[] reads(T)() { return readln.split.to!(T[]); }
alias readint = read!int;
alias readints = reads!int;