D = {i:chr(i+64) for i in range(1,27)}
N = int(input())
ans = []
x = N+1
while x>0:
    k = x%26
    if k>0:
        ans.append(D[k])
    else:
        ans.append(D[26])
        x -= 26
    x = x//26
ans = ans[::-1]
print("".join(ans))