CF219C.Color Stripe

A colored stripe is represented by a horizontal row of $n$ square cells, each cell is pained one of $k$ colors. Your task is to repaint the minimum number of cells so that no two neighbouring cells are of the same color. You can use any color from 1 to $k$ to repaint the cells.

The first input line contains two integers $n$ and $k$ ( $1<=n<=5·10^{5}; 2<=k<=26$ ). The second line contains $n$ uppercase English letters. Letter "A" stands for the first color, letter "B" stands for the second color and so on. The first $k$ English letters may be used. Each letter represents the color of the corresponding cell of the stripe.

Print a single integer — the required minimum number of repaintings. In the second line print any possible variant of the repainted stripe.