题解 | #自守数#

while True:
    try:
        n = int(input())
        k = 0
        for i in range(n+1):
            a = i**2
            b = len(str(i))
            if b == 1:
                c = str(a)[-1]
            if b >= 2:
                c = str(a)[-b:]
            if int(c) == i:
                k += 1
        print(k)
    except:
        break