x = input()

x = sorted(x,reverse = True)

ans = False
for i in range(len(x)-1,1,-1):
    if x[i] != x[i-1]:
        x[i],x[i-1] = x[i-1],x[i]
        ans = True
        break

if ans :
    print("".join(x))
else:
    print(-1)