n=int(input())

def comparison_bunsuu(a,b,c,d):
    A=b*c
    B=a*d
    if A>B:
        return True
    else:
        return False

ans=0

for a in range(10):
    for b in range(10):
        if a==b:
            continue
        l=max(a,b)
        r=10**9+1
        while(r-l>1):
            p=(r+l)//2
            X=(a*p+b,p**2-1)
            if(comparison_bunsuu(X[1],X[0],n,1)):
                l=p
            else:
                r=p
        ans+=l-max(a,b)

print(ans)