Give you a integer number N (1 ≤ n ≤ 2 ∗ 10100). Please compute S = 11 + 22 + 33 + . . . + N N Give the last digit of S to me. Input Input file consists of several N’s, each N a line. It is ended with N = 0. Output For each N give a line containing only one digit, which is the last digit of S. Sample Input 1 2 3 0 Sample Output 1 5 2