Stones

public class Stones {
    public static void main(String[] args) {
        IO io = new IO();
        String s = io.next();
        char c = '?';
        int r = 0;
        for (int i = 0; i < s.length(); i++) {
            if (s.charAt(i) == c) {
                r++;
            }
            c = s.charAt(i);
        }
        System.out.println(r);
    }
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED

Test 15

Verdict: ACCEPTED