(Reduced Digit Sum) The reduced digit sum of a number is the sum of the digits. If the sum of the digits is greater than nine then the process is repeated. For example, the sum of the digits for 567 is 5+6+7=18 and the sum of the digits for 18 is 9, so the digit sum of 567 is 9.

The input consists of n (0<n<100) lines.
Each line consists of the integer (ranges from 0 to 10^9109).
The last line of input consists of Int(-1).

Output the reduced digit sum of the input number.