int alternatingCharacters(char* s) {
    int i=0,j,count=0;
    while(s[i]!='\0'){
    char ch = s[i];
    j=i+1;
    while(s[j]==s[i] && s[j]!='\0'){
        j++;
        i++;
        count++;
    }
    if(s[j]=='\0')
        break;
    i++;
  }
  return count;
}