n = int(input())

l = [i+1 for i in range(n)]

l2 = []
for i in l:
    l3 = []
    for j in range(1, i+1):
        if i % j == 0:
            l3.append(j)
    if len(l3) == 2:
        l2.append(i)

print(sum(l2))