p = []

for i in range(2,1001):
    cnt = 0
    for j in range(1,i+1):
        if i%j == 0:
            cnt +=1
    if cnt == 2:
        p.append(i)


n = int(input())

ls = [i for i in p if i <= n]

sm = 0
for i in ls:
    sm += i
print(sm)