#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main() {
    cin.sync_with_stdio(false);
    cin.tie(nullptr);

    int N, M;
    cin >> N >> M;
    vector<pair<int, int>> transferS(N);
    for (auto &e : transferS) {
        cin >> e.first >> e.second;
    }
    sort(transferS.begin(), transferS.end());
    int answer = 0, last = 1;
    for (auto e : transferS) {
        if (e.first > last) {
            answer += e.first - last;
        }
        last = max(last, e.second);
    }
    cout << answer + N - last << '\n';
}