def is_prime(n):
    n=abs(n)
    if n==2: return True
    if n<2 or n&1==0: return False
    return pow(2,n-1,n)==1

def main():
    N=int(input())
    sum=0
    for i in range(1,N):
        if is_prime(i)==True:
            sum+=i
    print(sum)

if __name__=="__main__":
    main()