str = list(input()) temp = list() for i in str: if str.count(i) >= 2: continue else: temp.append(i) if len(temp) > 0: print(temp[0]) else: print(-1)
str = list(input()) temp = list() for i in str: if str.count(i) >= 2: continue else: temp.append(i) if len(temp) > 0: print(temp[0]) else: print(-1)