n, d = io.read("*n", "*n")
if(d <= n) then
    for i = 1, d do io.write("A") end
    for i = d + 1, n do io.write("C") end
else
    for i = d + 1, 2 * n do io.write("A") end
    for i = 1, d - n do io.write("B") end
end