def is_prime(n):
    for i in range(2, n + 1):
        if i * i > n:
            break
        if n % i == 0:
            return False
    return n != 1
    
n = int(input())

table = []

for i in range(1,n+1):
    if is_prime(i):
        table.append(i)
    
print(sum(table))