Bijective numeration

import sys
import math

b = {'1': 1, '2': 2, '3': 3, '4': 4, '5': 5, '6': 6, '7': 7, '8': 8, '9': 9, 'A': 10}

count = int(input())
liste = []
for decimary in input().split():
    dec = sum([b[d]*10**k for k, d in enumerate(decimary[::-1])])
    liste.append(dec)

r = sum(liste)

print(r, file=sys.stderr)


result = []
u = r
while u > 0:
    k = int(math.log10(u))
    d = u // 10 ** k
    u -= d * 10 ** k
    d = 'A' if d == 1 else str(d)
    result.append(d)

r = ''.join([d for d in result])

print(result, file=sys.stderr)

print(r)