#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const ll MOD = 1000000007;
const long long INF = 1LL << 60;
#define rep(i,n) for(int i = 0; i < n; i++)
#define all(x) (x).begin(),(x).end()

int main() {
    int n, q, ans = 0;
    cin >> n >> q;
    vector<bool> a(n,0);
    rep(i,q){
        int l, r;
        cin >> l >> r;
        while(l<=r){
            if(a[l]) a[l] = false;
            else a[l] = true;
        }
    }
    for(bool x : a)
        if(x) ans++;
}