//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2")
//#pragma GCC optimize("Ofast","unroll-loops","inline")
#include<bits/stdc++.h>
#define ll long long
//#define int ll
#define pb push_back
#define pii pair<int,int>
#define MP make_pair
#define fi first
#define se second
using namespace std;
const int N=1e6+10,M=1e6+10,mod=998244353;
int n,m,U[N],V[N];
vector<int> G1[N],G2[N];
vector<pii> e[N];
int v1[N],v2[N];
queue<int> q;
bool vis[N],t[N];
bool dfs(int u){
	if(u==n) return 1;
	if(vis[u]) return 0;
	vis[u]=1;
	for(pii v:e[u]){
		if(dfs(v.fi)) return t[v.se]=1,1;
	}
	return 0;
}
signed main(){
//	freopen("a.in","r",stdin);
//	freopen("a.out","w",stdout);
	ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
	cin>>n>>m;
	int ans=0;
	for(int i=1;i<=m;i++) cin>>U[i]>>V[i],e[U[i]].pb(MP(V[i],i));
	for(int i=1;i<=n;i++) sort(e[i].begin(),e[i].end());
	if(!dfs(1)) return cout<<0<<'\n',0;
//	for(int i=1;i<=m;i++) cout<<t[i]<<' ';cout<<'\n';
	v1[1]=1,v2[n]=1;
	for(int i=1,u,v;i<=m;i++) if(t[i]){
		u=U[i],v=V[i];
		ans+=(v1[u]&&v2[v]);
		G1[u].pb(v);
		if(v1[u]&&!v1[v]){
			q.push(v);
			while(!q.empty()){
				int x=q.front();q.pop();
				if(v1[x]) continue;v1[x]=1;
				for(int y:G1[x]) if(!v1[y]) q.push(y);
			}
		}
		G2[v].pb(u);
		if(v2[v]&&!v2[u]){
			q.push(u);
			while(!q.empty()){
				int x=q.front();q.pop();
				if(v2[x]) continue;v2[x]=1;
				for(int y:G2[x]) if(!v2[y]) q.push(y);
			}
		}
	}
	for(int i=1,u,v;i<=m;i++) if(!t[i]){
		u=U[i],v=V[i];
		ans+=(v1[u]&&v2[v]);
		G1[u].pb(v);
		if(v1[u]&&!v1[v]){
			q.push(v);
			while(!q.empty()){
				int x=q.front();q.pop();
				if(v1[x]) continue;v1[x]=1;
				for(int y:G1[x]) if(!v1[y]) q.push(y);
			}
		}
		G2[v].pb(u);
		if(v2[v]&&!v2[u]){
			q.push(u);
			while(!q.empty()){
				int x=q.front();q.pop();
				if(v2[x]) continue;v2[x]=1;
				for(int y:G2[x]) if(!v2[y]) q.push(y);
			}
		}
	}
	cout<<ans<<'\n';
	return 0;
}
/*
5 6
1 2
2 3
1 3
2 5
3 5
3 4
*/