#include <iostream>
#include <map>
#include <set>
#include <queue>
#include <cmath>
#include <vector>
#include <string>
#include <algorithm>
#include <functional>
using namespace std;
#pragma warning (disable: 4996)

long long N, M;
long long B[1 << 19], C[1 << 19];
long long col[1 << 19];
vector<long long> X;
vector<long long> G[1 << 19];

int main() {
	// Step #1. 入力
	cin >> N >> M;
	for (int i = 1; i <= M; i++) {
		cin >> B[i] >> C[i];
		X.push_back(B[i]);
		X.push_back(C[i]);
	}

	// Step #2. 座標圧縮
	sort(X.begin(), X.end());
	X.erase(unique(X.begin(), X.end()), X.end());
	for (int i = 1; i <= M; i++) B[i] = lower_bound(X.begin(), X.end(), B[i]) - X.begin();
	for (int i = 1; i <= M; i++) C[i] = lower_bound(X.begin(), X.end(), C[i]) - X.begin();
	for (int i = 1; i <= M; i++) G[C[i]].push_back(B[i]);

	// Step #3. 計算
	for (int i = 0; i < X.size(); i++) col[i] = -1;
	for (int i = X.size() - 1; i >= 0; i--) {
		if (col[i] != -1) continue;
		queue<int> Q; Q.push(i); col[i] = i;
		while (!Q.empty()) {
			int pos = Q.front(); Q.pop();
			for (int j : G[pos]) {
				if (col[j] == -1) { col[j] = i; Q.push(j); }
			}
		}
	}

	// Step #4. 答えを求める
	long long Answer = N * (N + 1LL) / 2LL;
	for (int i = 0; i < X.size(); i++) {
		Answer += (X[col[i]] - X[i]);
	}
	cout << Answer << endl;
	return 0;
}