def to_n(x,n,cnt):
    ans=[]
    for _ in range(cnt):
        ans.append(x%n)
        x//=n
    return ans[::-1]

from sys import stdin
def main():
    #入力
    readline=stdin.readline
    n=int(readline())

    alp=[chr(i) for i in range(65,65+26)]

    tmp=26
    cnt=1
    while n>=tmp:
        n-=tmp
        tmp*=26
        cnt+=1

    m=to_n(n,26,cnt)
    ans="".join([alp[m[i]] for i in range(cnt)])
    print(ans)

if __name__=="__main__":
    main()