def nta(N):
    if N==0:
        a="A"
    elif N==1: 
        a="B"
    elif N==2:
        a="C"
    elif N==3:
        a="D"
    elif N==4:
        a="E"
    elif N==5:
        a="F"
    elif N==6:
        a="G"
    elif N==7:
        a="H"
    elif N==8:
        a="I"
    elif N==9:
        a="J"
    elif N==10:
        a="K"
    elif N==11:
        a="L"
    elif N==12:
        a="M"
    elif N==13:
        a="N"
    elif N==14:
        a="O"
    elif N==15:
        a="P"
    elif N==16:
        a="Q"
    elif N==17:
        a="R"
    elif N==18:
        a="S"
    elif N==19:
        a="T"
    elif N==20:
        a="U"
    elif N==21:
        a="V"
    elif N==22:
        a="W"
    elif N==23:
        a="X"
    elif N==24:
        a="Y"
    elif N==25:
        a="Z"
    return a
Nu=int(input())
S=""
i=1
k=26
while k<Nu:
    k*=27
    i+=1
if i>1:
    k//=27
    i-=1
Q=Nu//k
if Q>0:
    S+=nta(Q-1)
R=Nu%k
while R>0 and k>26:
    k//=27
    Q=R//k
    S+=nta(R//k)
    R%=k
    i-=1
while i>=1:
    S+="A"
    i-=1
print (S)