N = int(input())
if N<=5:
    print(0)
else:
    P = list(range(N+1))
    for i in range(2,N+1):
        if i*i>N:break
        for j in range(i*i,N+1,i):
            P[j] = P[i]
    def phi(n):
        x = n
        C = {}
        while x>1:
            C[P[x]] = C.get(P[x],0)+1
            x //= P[x]
        cnt = n
        for p in C:
            cnt = cnt-cnt//p
        return cnt
    dp = [0]*(N+1)
    dp[3] = 1
    for i in range(4,N+1):
        dp[i] = dp[i-1]+phi(i)-1
    ans = 0
    for d in range(2,N//3+1):
        ans += dp[N//d]
    print(ans)