public class MinChange {
    public static void main(String[] args) {
        MinChange m = new MinChange();
        System.out.println(m.minChange("aaa"));

    }

    public int minChange(String input) {
        if (input == null || input.length() < 2) {
            return 0;
        }
        int[] dp = new int[input.length() + 1]; // length
        dp[0] = 0;
        dp[1] = 0;
        for (int i = 1; i < input.length(); i++) {
            if (input.charAt(i) == input.charAt(i - 1)) {
                dp[i + 1] = dp[i] + 1;
            } else {
                dp[i + 1] = dp[i];
            }
        }
        return dp[input.length()];
    }

}