#include <algorithm>
#include <cstdio>
#include <cstring>
#include <iostream>
#include <vector>
using namespace std;

typedef long long ll;

const int N = 1e6 + 5;

int n, m;
vector<int> son[N];
ll f[N];

ll dfs(int x) {
    if (f[x] != -1)
        return 1;
    f[x] = 0;
    for (auto y : son[x])
        f[x] += dfs(y);
    return f[x];
}

void solve() {
    cin >> n >> m;
    for (int i = 1; i <= m; i++) {
        int u, v;
        cin >> u >> v;
        son[v].push_back(u);
    }
    for (int i = 1; i <= n; i++)
        f[i] = -1;
    f[1] = 1;
    cout << dfs(n) << "\n";
}

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int T = 1;
    // cin >> T;
    while (T--) {
        solve();
    }
    return 0;
}