def dcf(x):
    a = []
    while x > 0:
        s = x % 10
        x //= 10
        a.insert(0, s)
    return a


n = int(input())
l = []
s = 0
c = 0

for i in range(10, n + 1):
    l = dcf(i)
    s = len(l)
    if s == 2 and l[0] == l[1]:
        c += 1
    elif s == 3 and l[0] == l[2]:
        c += 1
    elif s == 4 and l[0] == l[3] and l[1] == l[2]:
        c += 1
print(c + 9)
/**************************************************************
	Problem: 1149
	User: admin
	Language: Python
	Result: Accepted
	Time:191 ms
	Memory:34480 kb
****************************************************************/