code: func countSystematicChars(s string) int {
  	var x int
  	rs := []rune(s)
  
  	for i, c := range rs {
  		if i == 0 {
  			continue
  		}
  		if c == rs[i-1]+1 || c == rs[i-1]-1 {
  			x++
  		}
  	}
  
  	return x
  }
docs: // countSystematicChars returns how many runes in a string are part of a sequence ('abcdef', '654321')