If number formed by last three digits is divisible by 8.
int last = str [ n - 1 ] - '0' ; int second_last = str [ n - 2 ] - '0' ; int third_last = str [ n - 3 ] - '0' ; return ( ( third_last * 100 + second_last * 10 + last ) % 8 == 0 ) ; }