#include<stdio.h>
#include<string.h>
#define MAX 1100
int set[MAX];
int path[MAX];
int find(int fa)
{
	int t;
	int ch=fa;
	while(fa!=set[fa])
	fa=set[fa];
	while(ch!=fa)
	{
		t=set[ch];
		set[ch]=fa;
		ch=t;
	}
	return fa;
}
void mix(int x,int y)
{
	int fx,fy;
	fx=find(x);
	fy=find(y);
	if(fx!=fy)
	set[fx]=fy;
}
int main()
{
	int n,m,j,i,s,sum,a,b,wrong;
	while(scanf("%d",&n)&&n!=0)
	{
		scanf("%d",&m);
		memset(path,0,sizeof(path));
	//	memset(chu,0,sizeof(chu));
		for(i=1;i<=n;i++)
		set[i]=i;
		for(i=1;i<=m;i++)
		{
			scanf("%d%d",&a,&b);
			path[b]++;
			path[a]++;
			mix(a,b);
		}
		sum=0;wrong=0;
		for(i=1;i<=n;i++)
		{
			if(set[i]==i)
			{
				sum++;
				if(sum>1)
				{					
					wrong=1;
					break;
				}
			}
			if(path[i]!=2)
			{
				wrong=1;
				break;
			}
		}
		if(wrong)
		printf("0\n");
		else
		printf("1\n");
	}	
	return 0;
}