letters = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" digits = "0123456789"

for l1 in letters: for l2 in letters: for l3 in letters:

            for d1 in digits:
                for d2 in digits:
                    for d3 in digits:
                        for d4 in digits:
                            print (l1 + l2 + l3 + d1 + d2 + d3 + d4)

x=-b+-sqrt(b**2-4(a)(c))/2a