numbers = [10, 2, 21]

numbers_str = [str(n) for n in numbers]

for i in range(len(numbers_str)):
    for j in range(i+1, len(numbers_str)):
        if numbers_str[i] + numbers_str[j] < numbers_str[j] + numbers_str[i]:
            numbers_str[i],numbers_str[j] = numbers_str[j],numbers_str[i]

answer = ''.join(numbers_str)
print(answer)