#327 alphabet
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=""
k=26
if Nu<k:
    S+=nta(Nu)
else:
    while Nu>=k:
        R=Nu%k
        S=nta(R)+S
        Nu-=R
        k*=26
    k//=26
    S=nta(Nu//k)+S
print(S)