endless walk

// Those who cannot remember the past are
// condemned to repeat it (use DP -_-)
// - George Santayana

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;

#define all(v) v.begin(),v.end()
#define rall(v) v.rbegin(),v.rend()
#define ll long long
#define ull unsigned long long
#define MOD 1000000007
#define PI 3.14159265
#define ceil(a, b) ((a / b) + (a % b ? 1 : 0))
#define imin INT_MIN
#define imax INT_MAX
#define inf 2000000000
#define nl '\n'
#define ppcnt __builtin_popcount
#define ppcntll __builtin_popcountll
#define clz __builtin_clz
#define clzll __builtin_clzll
#define ctz __builtin_ctz
#define ctzll __builtin_ctzll
#define modulo(a, b, mod) ((((a) % mod) * ((b) % mod)) % mod)
#define cnte(v, x) count(all(v), (x))
#define mine(v) min_element(all(v))
#define maxe(v) max_element(all(v))
#define debug(x) cout << "x: " << x << nl;
#define debug2(x, y) cout << "x: " << x << " y: " << y << nl;
#define ordered_set tree<pair<int, int>, null_type, less<>, rb_tree_tag, tree_order_statistics_node_update>
#define ordered_map tree<int, int, less<>, rb_tree_tag, tree_order_statistics_node_update>

//vector<int> dx = {0, 0, 1, -1, 1, 1, -1, -1}, dy = {1, -1, 0, 0, 1, -1, 1, -1};
//vector<int> dx = {0, 0, 1, -1}, dy = {1, -1, 0, 0};

template<typename T = int> istream& operator>>(istream& in, vector<pair<int, int>>& v){
    for (auto& [x, y] : v) in >> x >> y;
    return in;
}

template<typename T = int> istream& operator>>(istream& in, vector<T>& v){
    for (T& i : v) in >> i;
    return in;
}

template<typename T = int> ostream& operator<<(ostream& out, const vector<T>& v){
    for (const T& x : v)
        out << x << ' ';
    return out;
}

template<typename T = pair<int, int>> ostream& operator << (ostream& out, const vector<pair<int, int>>& v){
    for(auto& [x, y] : v){
        out << x << ' ' << y << nl;
    }
    return out;
}

void Start_Crushing() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
#ifndef ONLINE_JUDGE
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif
}

vector<vector<int>> adj, rev;
vector<bool> vis;
vector<int> order;
set<int> component;
vector<set<int>> components;

void dfs1(int src){
    vis[src] = true;

    for(auto& nxt : adj[src]){
        if(not vis[nxt])
            dfs1(nxt);
    }
    order.emplace_back(src);
}

void dfs2(int src){
    vis[src] = true;
    component.insert(src);

    for(auto& nxt : rev[src]){
        if(not vis[nxt])
            dfs2(nxt);
    }
}

void solve(){
    int n, m; cin >> n >> m;
    adj.resize(n + 1), rev.resize(n + 1);

    while(m--){
        int u, v; cin >> u >> v;
        adj[u].emplace_back(v);
        rev[v].emplace_back(u);
    }

    vis.assign(n + 1, false);

    for(int i = 1; i <= n; i++)
        if(not vis[i])
            dfs1(i);


    vis.assign(n + 1, false);
    reverse(all(order));

    for(auto& i : order)
        if(not vis[i]){
            dfs2(i);

            if(component.size() > 1)
                components.emplace_back(component);

            component.clear();
        }

    vis.assign(n + 1, false);

    for(auto& c : components){
        for(auto& i : c)
            vis[i] = true;
    }

    int ans = 0;
    while(not order.empty()){
        for(auto& i : adj[order.back()]){
            if(vis[i]){
                ans++;
                vis[order.back()] = true;
                break;
            }
        }
        order.pop_back();
    }
    cout << ans;
}

int main(){
    Start_Crushing();

    int t = 1;
//    /*Multiple test cases?*/ cin >> t;
    while (t--) {
        solve();
        if(!t) break;
        cout << nl;
    }

//    for(int tc = 1; tc <= t; tc++){
//        cout << "Case #" << tc << ": ";
//        solve();
//        if(tc != t)
//            cout << nl;
//    }

    return 0;
}