#include using namespace std; using ll = long long; using VI = vector; using VL = vector; using VS = vector; using VB = vector; using VVB = vector>; using VVI = vector; using VVL = vector; using PII = std::pair; using VPII = std::vector>; using PLL = std::pair; using VPLL = std::vector>; using TI3 = std::tuple; using TI4 = std::tuple; using TL3 = std::tuple; using TL4 = std::tuple; #define rep(i, n) for (int i = 0; i < (int)(n); i++) #define repr(i, n) for (int i = (int)(n)-1; i >= 0; i--) #define rep2(i, s, n) for (int i = (s); i < (int)(n); i++) #define rep3(i, s, n, d) for (int i = (s); i < (int)(n); i += (d)) #define allpt(v) (v).begin(), (v).end() #define allpt_c(v) (v).cbegin(), (v).cend() #define allpt_r(v) (v).rbegin(), (v).rend() #define allpt_cr(v) (v).crbegin(), (v).crend() const int mod1 = 1e9 + 7, mod2 = 998244353, mod3 = 1e9 + 9; const int mod = mod1; const ll inf = 1e18; const string wsp = " "; const string tb = "\t"; const string rt = "\n"; const string alphabets = "abcdefghijklmnopqrstuvwxyz"; template void show1dvec(const vector &v) { if (v.size() == 0) return; int n = v.size() - 1; rep(i, n) cout << v[i] << wsp; cout << v[n] << rt; return; } template void show2dvec(const vector> &v) { int n = v.size(); rep(i, n) show1dvec(v[i]); } template void show1dpair(const vector> &v) { int n = v.size(); rep(i, n) cout << v[i].first << wsp << v[i].second << rt; return; } template void pairzip(const vector> &v, vector &t, vector &s) { int n = v.size(); rep(i, n) { t.push_back(v[i].first); s.push_back(v[i].second); } return; } template void maxvec(vector &v) { T s = v[0]; int n = v.size(); rep(i, n - 1) { if (s > v[i + 1]) { v[i + 1] = s; } s = v[i + 1]; } } template bool myfind(T t, S s) { return find(t.cbegin(), t.cend(), s) != t.cend(); } bool check(int y, int x, int h, int w) { return 0 <= y && y < h && 0 <= x && x < w; } bool iskadomatsu(int a, int b, int c) { return (a != b && b != c && c != a) && ((a > b && b < c) || (a < b && b > c)); } double euc_dist(PII a, PII b) { return sqrt(pow(a.first - b.first, 2) + pow(a.second - b.second, 2)); } VS split(string s, char c) { VS ret; string part; s += c; rep(i, s.length()) { if (s[i] == c) { ret.emplace_back(part); part = ""; } else if (s[i] != c) { part += s[i]; } } return ret; } template ll pow_mod(T p, S q, R mod = 1ll) { ll ret = 1, r = p; while (q) { if (q % 2) ret *= r, ret %= mod; r = (r * r) % mod, q /= 2; } return ret % mod; } template ll pow_no_mod(T p, S q) { ll ret = 1, r = p; while (q) { if (q % 2) ret *= r; r = (r * r), q /= 2; } return ret; } void make_frac_tables(VL &frac_list, VL &frac_inv_list) { rep(i, frac_list.size() - 1) { frac_list[i + 1] *= frac_list[i] * (i + 1); frac_list[i + 1] %= mod; frac_inv_list[i + 1] *= frac_inv_list[i] * pow_mod(i + 1, mod - 2, mod); frac_inv_list[i + 1] %= mod; } } pair make_frac_tables(int n) { VL frac_list(n + 1, 1), frac_inv_list(n + 1, 1); rep(i, n) { frac_list[i + 1] *= frac_list[i] * (i + 1); frac_list[i + 1] %= mod; frac_inv_list[i + 1] *= frac_inv_list[i] * pow_mod(i + 1, mod - 2, mod); frac_inv_list[i + 1] %= mod; } return make_pair(frac_list, frac_inv_list); } ll comb(int a, int b, const VL &frac_list, const VL &frac_inv_list) { if (a < b) return 0; if (b < 0) return 0; ll ret = frac_list[a]; ret *= frac_inv_list[b]; ret %= mod; ret *= frac_inv_list[a - b]; ret %= mod; return ret; } void djkstra(int n, int s, int t, const vector> &connect) { const int intm = 1e9; vector shortest(n, intm); shortest[s] = 0; vector search = {s}; vector new_search; while (!search.empty()) { for (auto i : search) { for (auto j : connect[i]) { if (shortest[j] > 1 + shortest[i]) { shortest[j] = 1 + shortest[i]; new_search.emplace_back(j); } } } search.clear(); search = new_search; new_search.clear(); // show1dvec(search); // show1dvec(shortest); } if (shortest[t] == intm) shortest[t] = -1; printf("%d\n", shortest[t]); } template void coordinate_compress(vector &x, map &zip, int &xs) { sort(x.begin(), x.end()); x.erase(unique(x.begin(), x.end()), x.end()); xs = x.size(); for (int i = 0; i < xs; i++) { zip[x[i]] = i; } } void dfs(int i, const VVI &connect, VI &maxvec) { for (auto j : connect[i]) if (maxvec[j] < maxvec[i]) { maxvec[j] = maxvec[i]; dfs(j, connect, maxvec); } } int main() { // cin.tie(0); // ios::sync_with_stdio(false); #ifdef DEBUG cout << "DEBUG MODE" << endl; ifstream in("input.txt"); // for debug cin.rdbuf(in.rdbuf()); // for debug #endif int n, m, a, b, k; cin >> n >> m; ll ans = n; ans = ans * (ans + 1) / 2; VPII node(m); VI use_node; map xzip; rep(i, m) { cin >> a >> b; node[i] = make_pair(a, b); use_node.emplace_back(a); use_node.emplace_back(b); } coordinate_compress(use_node, xzip, k); VVI connect(k); VI maxvec(k); iota(allpt(maxvec), 0); for (auto [a, b] : node) { connect[xzip[b]].push_back(xzip[a]); } repr(i, k) { if (maxvec[i] == i) { dfs(i, connect, maxvec); } } // cout << ans << rt; // show1dvec(maxvec); // show1dvec(use_node); rep(i, k) { ans += use_node[maxvec[i]] - use_node[i]; } cout << ans << rt; return 0; }