def min_operations_to_zero(N):

    dp = [float('inf')] * (N + 1)
    dp[0] = 0

    for i in range(1, N + 1):
        if i >= 2:
            dp[i] = min(dp[i], dp[i - 2] + 1)
        if i >= 3:
            dp[i] = min(dp[i], dp[i - 3] + 1)

    return dp[N]

N = int(input())
print(min_operations_to_zero(N))