//A tree without skin will surely die.
//A man without face will be alive.
#include<bits/stdc++.h>
using namespace std;
#define int long long
#define mid ((l+r)>>1)
#define lowbit(x) (x&-x)
#define all(x) (x).begin(),(x).end()
#define rep(i,j,k) for (int i=j;i<=k;++i)
#define per(i,j,k) for (int i=j;i>=k;--i)
int const N=1e6+10;
int n,m,rd[N],dp[N],vis[N],Rd[N],Vis[N];
vector<int>a[N];
inline int connectto(int x){
    if (x==n) return 1;
    if (vis[x]) return vis[x];
    for (auto v:a[x])
        if (connectto(v)==1) return vis[x]=1;
    return vis[x]=-1;
}
inline void solve(){
    cin>>n>>m;
    while (m--){
        int x,y;cin>>x>>y;
        a[x].push_back(y);
        ++Rd[y];
    }
    queue<int>Q;
    Q.push(1);
    while (!Q.empty()){
        int x=Q.front();Q.pop();
        Vis[x]=1;
        for (auto v:a[x])
            if (!Vis[v]) Vis[v]=1,Q.push(v);
    }
    rep(i,1,n){
        if (!connectto(i) || !Vis[i]) continue;
        for (auto j:a[i]) ++rd[j];
    }
    dp[1]=1;
    queue<int>q;q.push(1);
    while (!q.empty()){
        int x=q.front();q.pop();
        for (auto v:a[x]){
            if (connectto(v)==-1) continue;
            dp[v]+=dp[x],dp[x]=1;
            if (!--rd[v]) q.push(v);
        }
    }
    cout<<dp[n]<<'\n';
}
signed main(){
    ios::sync_with_stdio(false);
    cin.tie(0),cout.tie(0);
    int t=1;
    // cin>>t;
    while (t--) solve();
    cerr<<"Time: "<<(double)clock()/CLOCKS_PER_SEC<<" s\n";
    return 0;
}