//Let's join Kaede Takagaki Fan Club !! #pragma GCC optimize("Ofast") #pragma GCC optimize("unroll-loops") #include <cstdio> #include <cstring> #include <cstdlib> #include <cmath> #include <ctime> #include <cassert> #include <string> #include <algorithm> #include <vector> #include <queue> #include <stack> #include <functional> #include <iostream> #include <map> #include <set> #include <unordered_map> #include <unordered_set> #include <cassert> #include <iomanip> #include <chrono> #include <random> #include <bitset> #include <complex> #include <ext/pb_ds/assoc_container.hpp> #include <ext/pb_ds/tree_policy.hpp> using namespace std; #define int long long //#define L __int128 typedef long long ll; typedef pair<int,int> P; typedef pair<int,P> P1; typedef pair<P,P> P2; #define pu push #define pb push_back #define eb emplace_back #define mp make_pair #define eps 1e-7 #define INF 1000000000 #define a first #define b second #define fi first #define sc second //#define rng(i,a,b) for(int i=(int)(a);i<(int)(b);i++) #define rep(i,x) for(int i=0;i<x;i++) #define repn(i,x) for(int i=1;i<=x;i++) #define SORT(x) sort(x.begin(),x.end()) #define ERASE(x) x.erase(unique(x.begin(),x.end()),x.end()) #define POSL(x,v) (lower_bound(x.begin(),x.end(),v)-x.begin()) #define POSU(x,v) (upper_bound(x.begin(),x.end(),v)-x.begin()) #define all(x) x.begin(),x.end() #define si(x) int(x.size()) #define pcnt(x) __builtin_popcountll(x) #ifdef LOCAL #define dmp(x) cerr<<__LINE__<<" "<<#x<<" "<<x<<endl #else #define dmp(x) void(0) #endif template<class t,class u> bool chmax(t&a,u b){if(a<b){a=b;return true;}else return false;} template<class t,class u> bool chmin(t&a,u b){if(b<a){a=b;return true;}else return false;} template<class t> using vc=vector<t>; template<class t,class u> ostream& operator<<(ostream& os,const pair<t,u>& p){ return os<<"{"<<p.fi<<","<<p.sc<<"}"; } template<class t> ostream& operator<<(ostream& os,const vc<t>& v){ os<<"{"; for(auto e:v)os<<e<<","; return os<<"}"; } //https://codeforces.com/blog/entry/62393 struct custom_hash { static uint64_t splitmix64(uint64_t x) { // http://xorshift.di.unimi.it/splitmix64.c x += 0x9e3779b97f4a7c15; x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9; x = (x ^ (x >> 27)) * 0x94d049bb133111eb; return x ^ (x >> 31); } size_t operator()(uint64_t x) const { static const uint64_t FIXED_RANDOM = chrono::steady_clock::now().time_since_epoch().count(); return splitmix64(x + FIXED_RANDOM); } //don't make x negative! size_t operator()(pair<int,int> x)const{ return operator()(uint64_t(x.first)<<32|x.second); } }; //unordered_set -> dtype, null_type //unordered_map -> dtype(key), dtype(value) using namespace __gnu_pbds; template<class t,class u> using hash_table=gp_hash_table<t,u,custom_hash>; template<class T> void g(T &a){ cin >> a; } template<class T> void o(const T &a,bool space=false){ cout << a << (space?' ':'\n'); } //ios::sync_with_stdio(false); const ll mod = 998244353; //const ll mod = 1000000007; mt19937_64 mt(chrono::steady_clock::now().time_since_epoch().count()); template<class T> void add(T&a,T b){ a+=b; if(a >= mod) a-=mod; } ll modpow(ll x,ll n){ ll res=1; while(n>0){ if(n&1) res=res*x%mod; x=x*x%mod; n>>=1; } return res; } #define _sz 1 ll F[_sz],R[_sz]; void make(){ F[0] = 1; for(int i=1;i<_sz;i++) F[i] = F[i-1]*i%mod; R[_sz-1] = modpow(F[_sz-1], mod-2); for(int i=_sz-2;i>=0;i--) R[i] = R[i+1] * (i+1) % mod; } ll C(int a,int b){ if(b < 0 || a < b) return 0; return F[a]*R[b]%mod*R[a-b]%mod; } int n,m; vector<int>e[100005],f[100005]; int c[100005],p[100005],k; bool u[100005]; void dfs(int v){ if(u[v]) return; u[v] = 1; for(int i=0;i<e[v].size();i++){ if(!u[e[v][i]]) dfs(e[v][i]); } c[k++] = v; } void sfd(int v){ if(u[v]) return; u[v] = 1; p[v] = k; for(int i=0;i<f[v].size();i++){ if(!u[f[v][i]]) sfd(f[v][i]); } } void solve(){ cin>>n>>m; for(int i=0;i<m;i++){ int a,b; cin>>a>>b; e[a].push_back(b); f[b].push_back(a); } for(int i=1;i<=n;i++){ if(!u[i]){ dfs(i); } } memset(u,0,sizeof(u)); k=0; for(int i=n-1;i>=0;i--){ if(!u[c[i]]){ sfd(c[i]); k++; } } memset(u,0,sizeof(u)); vc<int>in(k), out(k); repn(i,n)for(auto x:e[i]){ if(p[i] != p[x]){ out[p[i]] ++; in[p[x]] ++; } } int ii = 0, oo = 0; rep(i, k){ if(in[i]==0)ii++; if(out[i]==0) oo++; } if(k == 1){ o(0); } else o(max(ii,oo)); } signed main(){ cin.tie(0); ios::sync_with_stdio(0); cout<<fixed<<setprecision(20); int t; t = 1; //cin >> t; while(t--) solve(); }