Vanya got an important task — he should enumerate books in the library and label each book with its number. Each of the *n* books should be assigned with a number from 1 to *n*. Naturally, distinct books should be assigned distinct numbers.

Vanya wants to know how many digits he will have to write down as he labels the books.
The first line contains integer *n* (1 ≤ *n* ≤ 10<sup class="upper-index">9</sup>) — the number of books in the library.
n = input()
a = int(n[-1])
chind = -1
for i in range(len(n)):
    if int(n[i]) % 2 == 0 and int(n[i]) < a:
        n = n[:i]+str(a)+n[i+1:-1]+n[i]
        print(n)
        exit()
    elif int(n[i]) % 2 == 0:
        chind = i
if chind == -1:
    print(chind)
else:   
    n = n[:chind]+str(a)+n[chind+1:-1]+n[chind]
    print(n)