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

int main() {
	cin.tie(0)->sync_with_stdio(0);

	int n, m; cin >> n >> m;
	vector adj(n, vector(0, 0));

	while (m--) {
		int a, b; cin >> a >> b; a--, b--;
		adj[a].emplace_back(b);
	}

	vector dp(n, -1);
	int ans = 0;
	auto dfs = [&](auto &self, int v) -> bool {
		if (v == n-1) return ans = 1;
		if (dp[v] != -1) return dp[v];

		dp[v] = 0;
		for (int u : adj[v]) if (self(self, u)) {
			ans += dp[v];
			dp[v] = 1;
		}

		return dp[v];
	};
	dfs(dfs, 0);
	cout << ans << '\n';
}