correct the text:
You are given a string s. if s[i]  is a  letter, reverse its case from lower to upper or vise versa, otherw ise k eep ita s it is . Ifthe stringcontains no lette rs,  reverse the s tring. Th e function shouldreturn t heresultedstring. Exampl es solv e("1234 ") = "432 1"   solve("ab") = "AB" solve("#a@C") = "#A@c "