#include <bits/stdc++.h>#define N 100010 using namespace std;int dep[N], low[N], st[N], top, cnt, blg[N], sz[N], f1[N], f2[N], d1[N], d2[N];int Number;bool ins[N];struct Node {int x, y;
}e[N];struct Edge {int head[N], to[N << 1], nxt[N << 1], tot;inline void add(int x, int y) {to[ ++ tot] = y;nxt[tot] = head[x];head[x] = tot;}
}G1,G2,G3;char *p1, *p2, buf[100000];#define nc() (p1 == p2 && (p2 = (p1 = buf) + fread(buf, 1, 100000, stdin), p1 == p2) ? EOF : *p1 ++ )int rd() {int x = 0, f = 1;char c = nc();while (c < 48) {if (c == '-')f = -1;c = nc();}while (c > 47) {x = (((x << 2) + x) << 1) + (c ^ 48), c = nc();}return x * f;
}void tarjan(int p) {st[ ++ top] = p;ins[p] = true;low[p] = dep[p] = ++cnt;for (int i = G1.head[p]; i; i = G1.nxt[i]) {if (!dep[G1.to[i]])tarjan(G1.to[i]), low[p] = min(low[p], low[G1.to[i]]);else if (ins[G1.to[i]])low[p] = min(low[p], dep[G1.to[i]]);}if (dep[p] == low[p]) {int t;Number ++ ;do {t = st[top -- ];ins[t] = false;blg[t] = Number;sz[Number] ++ ;} while(t != p);}
}queue<int> q;void dp1() {while (!q.empty()) {q.pop();}memset(f1, 0xef, sizeof f1);for (int i = 1; i <= Number; i ++ ) {if (!d1[i]) {q.push(i);}}f1[blg[1]] = 0;while (!q.empty()) {int x = q.front();q.pop();f1[x] += sz[x];for (int i = G2.head[x]; i; i = G2.nxt[i]) {f1[G2.to[i]] = max(f1[G2.to[i]], f1[x]);d1[G2.to[i]] -- ;if (!d1[G2.to[i]]) {q.push(G2.to[i]);}}}
}void dp2() {while (!q.empty()) {q.pop();}for (int i = 1; i <= Number; i ++ ) {if (!d2[i]) {q.push(i);}}memset(f2, 0xef, sizeof f2);f2[blg[1]] = 0;while (!q.empty()) {int x = q.front();q.pop();f2[x] += sz[x];for (int i = G3.head[x]; i; i = G3.nxt[i]) {f2[G3.to[i]] = max(f2[G3.to[i]], f2[x]);d2[G3.to[i]] -- ;if (!d2[G3.to[i]]) {q.push(G3.to[i]);}}}
}int main() {int n = rd(), m = rd();if (!n)puts("1"), exit(0);for (int i = 1; i <= m; i ++ ) {e[i].x = rd(), e[i].y = rd();G1.add(e[i].x, e[i].y);}for (int i = 1; i <= n; i ++ ) {if (!dep[i]) {tarjan(i);}}// for (int i = 1; i <= n; i ++ ) {//     printf("%d ",blg[i]);// }// puts("");for (int i = 1; i <= m; i ++ ) {e[i].x = blg[e[i].x];e[i].y = blg[e[i].y];if (e[i].x != e[i].y) {// printf("%d %d\n", e[i].x, e[i].y);G2.add(e[i].x, e[i].y);d1[e[i].y] ++ ;G3.add(e[i].y, e[i].x);d2[e[i].x] ++ ;}}dp1();dp2();// for (int i = 1; i <= Number; i ++ ) {//     printf("%d %d\n", f1[i], f2[i]);// }int ans = sz[blg[1]];for (int i = 1; i <= m; i ++ ) {if (e[i].x != e[i].y) {ans = max(ans, f1[e[i].y] + f2[e[i].x] - sz[blg[1]]);}}cout << ans << endl ;return 0;
}