n2a=lambda x:chr(x+ord("a"))
n=int(input())
"""
0,A,B,C,...,Z,
A=0
Z=25
AA=26=26+0
AB=26+1
ZZ=26+26**2-1
AAA=26+26**2+0
ZZZ=26+26**2+26**3-1
AAAA=26+26**2+26**3+0
26べきの和の部分と26進数の部分
"""
m=n
ary=[]
for i in range(1,100):
    if n-pow(26,i)<0:
        # i桁の列
        for _ in range(i):
            ary.append(n%26)
            n//=26
        break
    else:
        n-=pow(26,i)
ary.reverse()
ary=[n2a(x).upper() for x in ary]
print("".join(ary))