hoge,ans = [],[]
for i in range(2,10000):
for j in range(2,i):
if i % j == 0: break
else:hoge.append(i)
qqq = int(raw_input())
i,tt = 0,0
while qqq > 1:
if qqq % hoge[i] == 0:
tt+=hoge[i]
qqq/=hoge[i]
continue
i+=1
print tt
aG9nZSxhbnMgPSBbXSxbXQpmb3IgaSBpbiByYW5nZSgyLDEwMDAwKToKICBmb3IgaiBpbiByYW5nZSgyLGkpOgogICAgaWYgaSAlIGogPT0gMDogYnJlYWsKICBlbHNlOmhvZ2UuYXBwZW5kKGkpCnFxcSA9IGludChyYXdfaW5wdXQoKSkKaSx0dCA9IDAsMAp3aGlsZSBxcXEgPiAxOgogIGlmIHFxcSAlIGhvZ2VbaV0gPT0gMDogCiAgICB0dCs9aG9nZVtpXSAKICAgIHFxcS89aG9nZVtpXSAKICAgIGNvbnRpbnVlCiAgaSs9MQpwcmludCB0dA==