def next_bigger(n):
    num_string = list(str(n))
 
    for i, num in enumerate(num_string):
 
        if i == len(num_string)-1:
            return -1
 
        #find two the two numbers one bigger than the other with the minimun order
        if num_string[-i-1] > num_string[-i-2]:
            aux = num_string[-i-1]
 
            #interchange the locations:
            num_string[-i-1] = num_string[-i-2]
            num_string[-i-2] = aux
 
            # create a string from the list
            return int("".join(num_string))
 
print(next_bigger(231))

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