#include<cstdio>

 #include<cstring>

 #include<algorithm>

 #include<queue>

 #define rd read()

 using namespace std;

 const int N = 1e5 + ;

 const int inf = ~0U >> ;

 int n, m;

 int head[N], tot, Head[N], Tot;

 int low[N], dfn[N], cnt;

 int st[N], tp, col, c[N], val[N], subsz[N], upsz[N], deg[N], bvis[N];

 bool vis[N];

 struct edge {

     int nxt, fr, to;

 }e[N], E[N];

 queue<int> q;

 int read() {

     int X = , p = ; char c = getchar();

     for (; c > '' || c < ''; c = getchar())

         if (c == '-') p = -;

     for (; c >= '' && c <= ''; c = getchar())

         X = X *  + c - '';

     return X * p;

 }

 void add(int u, int v) {

     e[++tot].to = v;

     e[tot].fr = u;

     e[tot].nxt = head[u];

     head[u] = tot;

 }

 void Add(int u, int v) {

     E[++Tot].to = v;

     E[Tot].fr = u;

     E[Tot].nxt = Head[u];

     Head[u] = Tot;

 }

 void cmin(int &A, int B) {

     if (A > B) A = B;

 }

 void cmax(int &A, int B) {

     if (A < B) A = B;

 }

 void tarjan(int u) {

     dfn[u] = low[u] = ++cnt;

     vis[u] = ; st[++tp] = u;

     for (int i = head[u]; i; i = e[i].nxt) {

         int nt = e[i].to;

         if (!dfn[nt]) {

             tarjan(nt);

             cmin(low[u], low[nt]);

         }

         else if (vis[nt]) cmin(low[u], dfn[nt]);

     }

     if (low[u] == dfn[u]) {

         col++;

         for (; tp;) {

             int z = st[tp--];

             c[z] = col;

             vis[z] = ;

             val[col]++;

             if (z == u) break;

         }

     }

 }

 void dfs(int u) {

     vis[u] = ;

     for (int i = Head[u]; i; i = E[i].nxt) {

         int nt = E[i].to;

         dfs(nt);

     }

 }

 int dfs2(int u) {

     if (bvis[u] == ) return ;

     if (bvis[u] == -) return ;

     if (u == c[]) return ;

     bool flag = false;

     for (int i = Head[u]; i; i = E[i].nxt) {

         int nt = E[i].to;

         if (dfs2(nt)) {

             flag = true;

             cmax(upsz[u], upsz[nt] + val[u]);

         }

     }

     bvis[u] = flag ?  : -;

     return flag;

 }

 void Topsort() {

     subsz[c[]] = val[c[]];

     for (int i = ; i <= col; ++i)

         if (!deg[i]) q.push(i);

     for (int u; !q.empty(); ) {

         u = q.front(); q.pop();

         for (int i = Head[u]; i; i = E[i].nxt) {

             int nt = E[i].to;

             if (subsz[u] != -inf)

                 cmax(subsz[nt], subsz[u] + val[nt]);

             deg[nt]--;

             if (!deg[nt]) q.push(nt);

         }

     }

 }

 int main()

 {

     n = rd; m = rd;

     for (int i = ; i <= m; ++i) {

         int u = rd, v = rd;

         add(u, v);

     }

     for (int i = ; i <= n; ++i)

         if (!dfn[i]) tarjan(i);

     for (int i = ; i <= m; ++i) {

         int u = e[i].fr, v = e[i].to;

         u = c[u], v = c[v];

         if (u == v) continue;

         Add(u, v);

         deg[v]++;

     }

     memset(vis, , sizeof(vis));

     for (int i = ; i <= col; ++i) subsz[i] = -inf;

     dfs(c[]);

     Topsort();

     bvis[c[]] = ;

     upsz[c[]] = val[c[]];

     for (int i = ; i <= col; ++i)

         if (!vis[i]) dfs2(i);

     int ans = val[c[]];

     for (int i = ; i <= m; ++i) {

         int u = e[i].fr, v = e[i].to;

         u = c[u]; v = c[v];

         if (u == v) continue;

         if (!vis[v] || !(bvis[u] == )) continue;

         cmax(ans, subsz[v] + upsz[u] - val[c[]]);

     }

     printf("%d\n", ans);

 }