import sys input = sys.stdin.buffer.readline sys.setrecursionlimit(10 ** 7) class SCC_graph(object): def __init__(self, n): """n:ノード数""" self.n = n self.edges = [] def add_edge(self, frm, to): """frm -> toへ有効辺を張る""" self.edges.append((frm, to)) def __csr(self): self.start = [0] * (self.n + 1) self.elist = [0] * len(self.edges) for frm, to in self.edges: self.start[frm + 1] += 1 for i in range(1, self.n + 1): self.start[i] += self.start[i - 1] cnt = self.start[:] for frm, to in self.edges: self.elist[cnt[frm]] = to cnt[frm] += 1 def __dfs(self, v): self.low[v] = self.now_ord self.order[v] = self.now_ord self.now_ord += 1 self.visited.append(v) for i in range(self.start[v], self.start[v + 1]): to = self.elist[i] if self.order[to] == -1: self.__dfs(to) self.low[v] = min(self.low[v], self.low[to]) else: self.low[v] = min(self.low[v], self.order[to]) if self.low[v] == self.order[v]: while self.visited: u = self.visited.pop() self.order[u] = self.n self.ids[u] = self.group_num if u == v: break self.group_num += 1 def _make_scc_ids(self): self.__csr() self.now_ord = 0 self.group_num = 0 self.visited = [] self.low = [0] * self.n self.ids = [0] * self.n self.order = [-1] * self.n for i in range(self.n): if self.order[i] == -1: self.__dfs(i) for i in range(self.n): self.ids[i] = self.group_num - 1 - self.ids[i] def scc(self): self._make_scc_ids() groups = [[] for _ in range(self.group_num)] for i in range(self.n): groups[self.ids[i]].append(i) return groups, self.ids N, M = map(int, input().split()) BC = tuple(tuple(map(int, input().split())) for _ in range(M)) val = set() for b, c in BC: val.add(b) val.add(c) val = sorted(val) vtoi = {v: i for i, v in enumerate(val)} sz = len(val) G = SCC_graph(sz) for b, c in BC: s = vtoi[b] t = vtoi[c] G.add_edge(s, t) group, gtoi = G.scc() edge = [set() for _ in range(len(group))] for b, c in BC: s = gtoi[vtoi[b]] t = gtoi[vtoi[c]] edge[t].add(s) vmax = [0] * len(group) for s in reversed(range(len(group))): g = group[s] vmax[s] = max(vmax[s], max(g)) for t in edge[s]: vmax[t] = max(vmax[t], vmax[s]) ans = N * (N + 1) // 2 for v, g in zip(vmax, group): for i in g: ans -= val[i] ans += val[v] print(ans)