#include<iostream>
#include<algorithm>
#include<cstring>

using namespace std;

typedef pair<int,int> PII;

const int N = 100010;

int n,k;
int st[N];

int main()
{
    cin>>n>>k;
    int x,y;
    int res = 0;
    st[0] = 1;
    for(int i = 1; i<=k; i++)
    {
        cin>>x>>y;
        if(st[y] == 0)
        {
             res++;
             //cout<<i<<' ';
        }
        st[x] = 1;
    }
    cout<<res;
    return 0;
}