X = list(input())
if len(set(X)) == 1:
    print(-1)
    exit()
    
X.sort()
for i in range(len(X)-1):
    if X[i] == X[i+1]:
        continue
    if i+1 < len(X)-1:
        X[i],X[i+1] = X[i+1],X[i]
        print("".join(X[::-1]))
        exit()
print(-1)