N = int(input())
ans = ""

if 0 <= N < 26:
    print(chr(N % 26 + ord("A")))
else:
    while True:
        q = N // 26
        r = N % 26
    
        if q == 0:
            ans = chr(r + ord("A") - 1) + ans
            break
        else:
            ans = chr(r + ord("A")) + ans
            N = q
            
    print(ans)