table = list("abcdefghijklmnopqrstuvwxyz")
N = int(input())

ans = []
while True:
    ans.append(N%26)
    if N%26 == 0:
        N -= 1
    if  N//26 == 0:
        break
    N//=26
for x in reversed(ans):
    print(table[x-1],end='')

print()
