#include <bits/stdc++.h>

using namespace std;

const int lim = 100001;
int N, M, i;
vector<int> adj[lim];
bool visited[lim];
int cc = 0;

void dfs(int s)
{
    if (visited[s]) return;
    visited[s] = true;
    cc++;
    for (auto u : adj[s])
        dfs(u);
}

int main()
{
    cin >> N >> M;
    for (i = 0; i < M; i++)
    {
        int n, m;
        cin >> n >> m;
        adj[n].push_back(m);
    }

    dfs(1);

    cout << cc;

    return 0;
}