N = int(input())

v = N
arr = []
while v > 0:
    v, b = divmod(v, 26)
    arr.append(b)
arr.reverse()
if len(arr) > 1:
    arr[0] -= 1
if N == 0:
    ans = 'A'
else:
    ans = ''
for v in arr:
    ans += chr(v + ord('A'))
print(ans)