## https://yukicoder.me/problems/no/1185

MOD = 998244353



def main():
    N = int(input())
    answer = 0
    for n in range(10, min(99, N) + 1):
        if n % 3 == 0:
            answer += 1

    
    # 3桁以上の自然数について
    for bit in range(4 ** 10):
        number = 0
        for _ in range(10):
            number *= 10
            b = bit % 4
            number += 3 * b
            bit //= 4
        
        if number % 3 == 0 and number <= N and number >= 100:
            answer += 1
    print(answer)








if __name__ == "__main__":
    main()