#include<bits/stdc++.h>
using namespace std;
using ll = long long;

#define D if(0)

const int NMAX = 1123456;

struct Vr
{
	vector<Vr *> f,t;
	int odtoku=0;
	int prtoku=0;
};

int n,m;
Vr vr [NMAX];

int main()
{
	int out=0;
	scanf("%d%d",&n,&m);
	for(int i=0;i<m;i++)
	{
		int x,y;
		scanf("%d%d",&x,&y);
		x--;y--;
		vr[x].t.push_back(vr+y);
		vr[y].f.push_back(vr+x);
		vr[x].odtoku++;
		vr[y].prtoku++;
	}
	for(int i=0;i<n;i++)
	{
		for(Vr * it: vr[i].t)
		{
			if(vr[i].odtoku > 1 && it->prtoku > 1)
			{
				out++;
				vr[i].odtoku++;
				it->prtoku++;
			}
		}
	}
	printf("%d\n",out);
}