#include <bits/stdc++.h>
using namespace std;
#define int long long
#define endl '\n'
#define ii pair<int, int>
#define x first
#define y second
const int N = 1e5+5, M = 1e3+5, inf = 1e18, MOD = 998244353;
int n, m, x, y, res, k, cnt, sum, test;
int a[N], b[N], f[27][N][18], Min[N][27], d[N][27];
char c[N];

signed main(){
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    cin >> n;
    for (int i = 1; i <= 9; ++i) {
        x = 0;
        while (1) {
            x = x * 10 + i;
            if (x > n) break;
            ++res;
        }
    }
    x = 1;
    while (1) {
        x = x * 10;
        if (x > n) break;
        ++res;
    }
    cout << res;
}