[Baekjoon] 1065

a = 0

count = 0

a = int(input())

if (a < 100):

    print (a)

elif (99 < a < 1000):

    for i in range(99, a+1):

        if ((i // 100) + (i % 10) == 2 * (i % 100 // 10)):

            count += 1

    print (count+99)

elif (a == 1000) :

    print (144)

else :

    print ("범위를 넘어갔자나 인마")