N = int(input())
M = N
A = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
S = ""

if N <= 25:
    print(A[N])
    exit()

while N >= 26:
    S = A[((N//26)-1)%26] + S
    N //= 26
    N -= 1

print(S+A[M%26])