import string


N = int(input())
S = ''
T = ''
while True:
    if N < 26:
        S += string.ascii_uppercase[N]
        break
    else:
        t = 1
        while t * 27 - 1 < N:
            t *= 26
        S += (string.ascii_uppercase)[N % (t * 26) // t]
        T += (string.ascii_uppercase)[N % (t * 26) // t - 1]
        N -= N // t * t
if len(T) == 0:
    print(S)
else:
    print(T[0] + S[1:])