text: def marsExploration(s):
      s = list(s)
      t = 0
      
      for i in range(0, len(s), 3):
          if s[i] != "S":
              t += 1
          if s[i+1] != "O":
              t += 1
          if s[i+2] != "S":
              t += 1
      
      return t