#include<bits/stdc++.h>
using namespace std;
int n;
int dfs(vector<vector<int>>& v, vector<int>& dp, int node) {
    if (node == n)return 1;

    if (dp[node] != -1)return 1;
    
    auto& ret = dp[node];
    ret = 0;

    for (auto& to : v[node]) {
        ret += dfs(v, dp, to);
    }

    return ret;
}

signed main() {
    ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);

    cin >> n;
    int m;
    cin >> m;

    vector<vector<int>>v(n+1);
    vector<int>dp(n + 1,-1);
    while (m--) {
        int a, b;
        cin >> a >> b;
        v[a].push_back(b);

    }

    cout << dfs(v, dp, 1) << "\n";
}