#include<cstdio>
#include<vector>
#include<algorithm>
#include<map>
using namespace std;
const int MAX=(int)1e5;
class G{
public:
	vector<int>s;
	map<int,int>vis;
}a[MAX+100];
int d[MAX+100]={0};
int n,m,sum=0;
void dfs(int r){
	d[r]--;
	for(int i=0;i<a[r].s.size();i++){
		if(a[r].vis[a[r].s[i]]==0){
			a[r].vis[a[r].s[i]]=1;
			a[a[r].s[i]].vis[r]=1;
			d[r]--;
			dfs(a[r].s[i]);
			break;
		}
	}
}
int main(){
	freopen("sent.in","r",stdin);
	freopen("sent.out","w",stdout);
	scanf("%d%d",&n,&m);
	int x,y;
	for(int i=1;i<=m;i++){
		scanf("%d%d",&x,&y);
		a[x].s.push_back(y);
		a[y].s.push_back(x);
		a[x].vis[y]=0;
		a[y].vis[x]=0;
		d[x]++;d[y]++;
	}
	int l=1;
	for(;;){
		int minn=MAX+10,k=-1;
		for(int i=1;i<=n;i++){
			if(d[i]<minn&&d[i]!=0){
				minn=d[i];
				k=i;
			}
		}
		if(minn!=0){
			d[k]++;
			dfs(k);
		}
		bool flag=0;
		for(int i=l;i<=n;i++){
			if(d[i]!=0){
				flag=1;
				l=i;
				break;
			}
		}
		if(flag==0)
			break;
		else
			sum++;
	}
	printf("%d",sum);
	return 0;
}