عدد اختلاف

def maximum(a):
    b=a[0]
    c=0
    for i in range(1,len(a)):
        if a[i]>b:
            b=a[i]
            c=i
    return c
def tr(a):
    b=0
    while a!=0:
        a=a//10
        b=b+1
    return b
n=int(input())
a=(n-1)*[0]
for i in range(1,n):
    if i<9:
        a[i-1]=i
    else:
        b=tr(i+1)
        c=0
        for j in range(b-1):
            d=i//10**j%10
            e=i//10**(j+1)%10
            if d>e:
                c=c+d-e
            else:
                c=c+e-d
        a[i-1]=c
z=maximum(a)
print(z+1)