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

struct iofast_t {
    iofast_t() {
        ios::sync_with_stdio(false);
        cin.tie(nullptr);
    }
} iofast;

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...);
}

template <typename T, typename Compare = less<T>>
T &chmin(T &l, T r, Compare &&f = less<T>()) { return l = min(l, r, f); }
template <typename T, typename Compare = less<T>>
T &chmax(T &l, T r, Compare &&f = less<T>()) { return l = max(l, r, f); }

int main() {
    int n, m; cin >> n >> m;

    auto range = vec<tuple<int, int>>(uns, m);
    for (auto &[l, r] : range) {
        cin >> l >> r;
    }

    sort(begin(range), end(range), [&](auto x, auto y) {
        return get<1>(x) < get<1>(y);
    });

    auto used = vec<int>(uns, 0);
    for (auto [l, r] : range) {
        if (distance(lower_bound(begin(used), end(used), l), end(used)) != 0) {
            continue;
        }
        used.push_back(r);
    }

    cout << (n - size(used)) << endl;
}