#include <bits/stdc++.h>
using namespace std;
int arr[320000],brr[320000],t[320000];
int n,m;
void gcd(int k){
	for(int i=1;i<=m;i++){
		if(arr[i]==k){
			if(t[brr[i]]>=m){
				return;
			}
			t[brr[i]]++;
			gcd(brr[i]);
		}
	}
	return;
}
int main(){
	ios::sync_with_stdio(false);
	cin.tie(0),cout.tie(0);
	t[1]=1;
	cin>>n>>m;
	for(int i=1;i<=m;i++){
		cin>>arr[i]>>brr[i];
	}
	gcd(1);
	int ans=0;
	for(int i=1;i<=n;i++){
		if(t[i]>=1){
			ans++;
		}
	}
	cout<<ans;
}

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

MyAyCjIgMQozIDIK

3 2
2 1
3 2