n = int(input())
searchlist = list(range(2,n+1))
primelist = []
if n != 1:
    while searchlist[0]**2 <= n:
        primelist.append(searchlist[0])
        searchlist = [i for i in searchlist if i%primelist[-1]!=0]
    primelist.extend(searchlist)
    print(sum(primelist))
else:
    print(0)