Baekjoon 1065번(python)

num = int(input())

count = 0
for i in range(1, num + 1):
    if(len(str(i)) == 1 or len(str(i)) == 2):
        count += 1
    elif(len(str(i)) == 3):
        str_i = str(i)
        if(int(str_i[0]) - int(str_i[1]) == int(str_i[1]) - int(str_i[2])):
            count += 1
    elif(i == 1000):
        break

print(count)