#左から決めていく
#x >= 26:"A"を右端に追加
#x < 26:li[x]を右端に追加

li = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
N = input()
s = []
x = N

while x >= 0:
    if x >= 26:
        s += "A"
        x = x - 26
    else:
        s += li[x]
        x = -1
        
print "".join(s)