import math
plist = []

def isPrime(p):
    if p == 1:
        return False
    if p <= 3:
        plist.append(p)
        return True
    else:
        if p % 2 == 0:
            return False
        else:
            s = math.ceil(math.sqrt(p))

            isP = True
            for i in range(2, s+1):
                if p % i == 0:
                    isP = False

            if isP:
                plist.append(p)
            return isP

if __name__ == "__main__":
    n = int(input())

    for i in range(2, n+1):
        isPrime(i)

    print(sum(plist))