#include<bits/stdc++.h>
using namespace std;

#define V vector
#define pb push_back

int main() {
    int n, m;
    cin >> n >> m;
    V<V<int>> fr(n + 1);
    for(int i = 1; i <= m; i++) {
        int a, b; cin >> a >> b;
        fr[b].pb(a);
    }

    int ans = 1;
    V<int> reach(n + 1);
    V<int> cnt(n + 1);
    reach[1] = 1;
    cnt[1] = 1;
    for(int i = 2; i <= n; i++) {
        for(auto x : fr[i]) {
            if(!reach[x]) continue;
            if(cnt[x]) {
                cnt[i] += cnt[x], reach[i] = 1;
                cnt[x] = 0;
            } else cnt[i]++, reach[i] = 1;
        }
        // cout << cnt[i] << endl;
    }



    cout << cnt[n] << endl;


}