#include <bits/stdc++.h>
using namespace std;

struct uns_t {} uns;
template <typename Element, typename Head, typename ...Args>
auto vec(Element init, Head arg, Args ...args) {
    if constexpr (sizeof...(Args) == 0) return std::vector(arg, init);
    else return std::vector(arg, vec(init, args...));
}
template <typename Element, typename Head, typename ...Args>
auto vec(uns_t, Head arg, Args ...args) {
    return vec(Element(), arg, args...);
}

int main() {
    constexpr int64_t base = 1000000001;

    int64_t n; cin >> n;

    map<int, bool> used;
    auto btoi = [](int bits) {
        int ans = 0;
        while (bits) {
            ans *= 10;
            ans += bits & 1;
            bits >>= 1;
        }
        return ans;
    };

    int ans = 0;
    for (int i = 1; i < (1 << 9); ++i) {
        auto unit = btoi(i);
        if (used[unit]) continue;
        used[unit] = true;

        bool found = false;
        auto s = to_string(unit);
        auto beg1 = begin(s);
        auto beg2 = end(s) - 1;
        while (begin(s) != beg2 && end(s) != beg1) {
            if (*beg1 != *beg2) {
                found = true;
            }
            ++beg1; --beg2;
        }
        if (found) continue;

        for (int j = 1; j <= 9; ++j) {
            ans += base * j * unit <= n;
        }
    }

    cout << ans << endl;
}