#define _CRT_SECURE_NO_WARNINGS
#include"bits/stdc++.h"
#ifdef _DEBUG
#define DBG(n) n
#else
#define DBG(n)
#endif
#define INF         1e9
#define INFLL       1e18
#define EPS         1e-9
#define REP(i,n)    for(ll i=0,i##_len=(n);i<i##_len;++i)
#define REP1(i,n)   for(ll i=1,i##_len=(n);i<=i##_len;++i)
#define REPR(i,n)   for(ll i=(n)-1;i>=0;--i)
#define REPR1(i,n)  for(ll i=(n);i>0;--i)
#define REPC(i,obj) for(auto i:obj)
#define ALL(obj)    (obj).begin(),(obj).end()
#define SETP(n)     cout << fixed << setprecision(n)
using namespace std;
using ll = long long;
template<typename T = ll>inline T in() { T ret; cin >> ret; return ret; }

signed main() {
	int n = in(), m = in();
	vector<int>imos(n + 1);
	REP(i, m) {
		int c = in(), d = in();
		++imos[c];
		--imos[d];
	}
	REP(i, n)imos[i + 1] += imos[i];
	int len = 0;
	REP(i, n + 1)if (imos[i] != 0)++len;
	cout << n + len * 2 + 1 << endl;
}
