백준_BruteForce_한수

def check(n):
    numlist = []
    while(True):
        numlist.append(n % 10)
        n = n // 10
        if n == 0:
            break
    numlist.reverse()
    
    diff = 0
    for i in range(len(numlist)-1):
        if i == 0:
            diff = numlist[i+1] - numlist[i]
            continue
        new_diff = numlist[i+1] - numlist[i]
        if diff != new_diff:
            return False
    return True

n = int(input())
cnt = 0
for num in range(1,n+1):
    if check(num):
        cnt += 1
print(cnt)