import sys
sys.setrecursionlimit(10000000)
MOD = 10 ** 9 + 7
INF = 10 ** 15

def main():
    M = 1e9 + 1
    N = int(input())
    ans = 0
    for i in range(1,10):
        if i*M <= N:
            ans += 1
    for i in range(1,100000):
        s = str(i)
        X = int(s + s[::-1])
        if X*M <= N:
            ans += 1
        for a in '0123456789':
            X = int(s + a + s[::-1])
            if X*M <= N:
                ans += 1
    print(ans)
if __name__ == '__main__':
    main()