N = int(input())
ans = 0
for a1 in range(1,10):
    for a2 in range(10):
        for a3 in range(10):
            for a4 in range(10):
                for a5 in range(10):
                    M = a1*10**8+a2*10**7+a3*10**6+a4*10**5+a5*10**4+a4*10**3+a3*10**2+a2*10+a1
                    if M*(10**9+1)<=N:
                        ans += 1
for a1 in range(1,10):
    for a2 in range(10):
        for a3 in range(10):
            for a4 in range(10):
                M = a1*10**7+a2*10**6+a3*10**5+a4*10**4+a4*10**3+a3*10**2+a2*10+a1
                if M*(10**9+1)<=N:
                    ans += 1
                M = a1*10**6+a2*10**5+a3*10**4+a4*10**4+a3*100+a2*10+a1
                if M*(10**9+1)<=N:
                    ans += 1
for a1 in range(1,10):
    for a2 in range(10):
        for a3 in range(10):
            M = a1*10**5+a2*10**4+a3*1000+a3*100+a2*10+a1
            if M*(10**9+1)<=N:
                ans += 1
            M = a1*10**4+a2*1000+a3*100+a2*10+a1
            if M*(10**9+1)<=N:
                ans += 1
for a1 in range(1,10):
    for a2 in range(10):
        M = a1*1000+a2*100+a2*10+a1
        if M*(10**9+1)<=N:
            ans += 1
        M = a1*100+a2*10+a1
        if M*(10**9+1)<=N:
            ans += 1
for a1 in range(1,10):
    M = a1*10+a1
    if M*(10**9+1)<=N:
        ans += 1
    M = a1
    if M*(10**9+1)<=N:
        ans += 1
print(ans)