#include <iostream>
#include <cstring>
#include <algorithm>
using namespace std;
int n,k;
bool check[100010]={false};
int main()
{
cin>>n>>k;
int count=0;
check[0]=1;
while(k--)
{
int a,b;
cin>>a>>b;
if(check[b]==false) count++;
check[a]=true;
}
cout<<count<<endl;
return 0;
}