list1=[2,3,5,7,11,13,17,19]
N=int(input())
for i in range(21,1000):
    count=0
    for j in range(3,int(i/2)+1):
        if i%j==0:
            count=1
            break
        else:
            j+=2
    if  count==0:
        list1.append(i)
    else:
        count=0
ans=0
for k in range(len(list1)):
    if N>=list1[k]:
        ans+=list1[k]
print(ans)