def main():
    import sys
    input = sys.stdin.readline

    N = int(input())
    if N == 1:
        print(0)
        exit()

    prime = [True] * (N+1)
    prime[0] = False
    prime[1] = False
    for i in range(2, N+1):
        if prime[i]:
            for j in range(i*2, N+1, i):
                prime[j] = False

    ans = 1
    for r in range(3, N+1):
        if not prime[r]:
            continue
        if r**2 - 2 > N:
            break
        if prime[r**2 - 2]:
            ans += 2
    print(ans)


if __name__ == '__main__':
    main()