giải bằng python nhé!!!

$\color{#23d78c}{\texttt{P}}\color{#9ee36f}{\texttt{y}}\color{#10c1ed}{\texttt{t}}\color{#10c1ed}{\texttt{h}}\color{#c6ea64}{\texttt{o}}\color{#fbfb45}{\texttt{n}}$

n = int(input())
res=0
for i in range(1,10):
    for j in range(1,10):
        if (int(str(i)*j) <= n): res += 1
        else: break
print(res)

# Author : Daoanhviet96
# Language : Python3

$\\$
\begin{array}{c|c|c}\color{#ffd710}{\texttt{\{}} \color{#8655d6}{\texttt{\{}}\ \ \color{#8cdcda}{\text{Daoanhviet96}}\ \ \color{#8655d6}{\texttt{\}}} \color{#ffd710}{\texttt{\}}}\end{array}