func countSubstrings(s string) int {
	n, cnt := len(s), 0
	if n == 0 {
		return cnt
	}
	for i := range s {
		cnt++
		for j := 1; 0 <= i-j && i+j < n; j++ {
			if s[i-j] == s[i+j] {
				cnt++
			} else {
				break
			}
		}
		for j := 1; 0 <= i-j+1 && i+j < n; j++ {
			if s[i-j+1] == s[i+j] {
				cnt++
			} else {
				break
			}
		}
	}
	return cnt
}