#include<cstdio>
#include<algorithm>
#include<queue>
#define maxn 1000005
#define re register
using namespace std;

inline int read(){
	int s=0,f=1;
	char ch=getchar();
	while(ch<'0'||ch>'9'){
		if(ch=='-')f=-1;
		ch=getchar();
	}
	while(ch>='0'&&ch<='9'){
		s=(s<<1)+(s<<3)+ch-'0';
		ch=getchar();
	}
	return s*f;
}

int max(int x,int y){
	return x>y?x:y;
}

int min(int x,int y){
	return x<y?x:y;
}

int n,m,ans;

struct E{
	int y,nxt;
}edge[maxn];

int head[maxn],tot;

void add(int x,int y){
	edge[++tot].y=y;
	edge[tot].nxt=head[x];
	head[x]=tot;
}

int basea,baseb;

struct B{
	int x,y;
	friend bool operator < (B a,B b){
		if(a.x==b.x)return a.y<b.y;
		return a.x<b.x;
	}
}e[maxn];

int inn[maxn];

bool check[maxn],vis[maxn];

void toposort(){
	queue<int>q;
	for(re int i=1;i<=n;++i){
		if(inn[i]<3){
			q.push(i);
			check[i]=1;
		} 
	}
	while(!q.empty()){
		int x=q.front();
		q.pop();
		for(re int i=head[x];i;i=edge[i].nxt){
			int y=edge[i].y;
			//if(inn[y]==0)continue;
			if(check[y])continue;
			--inn[y];
			if(inn[y]<3){
				q.push(y);
				check[y]=1;
			}
		}
		//inn[x]=0;
	}
}

int main()
{
	freopen("asm_game.in","r",stdin);
	freopen("asm_game.out","w",stdout);
	n=read();
	m=read();
	for(re int i=1;i<=m;++i){
		int x=read();
		int y=read();
		add(x,y);
		add(y,x);
		inn[x]++;
		inn[y]++;
	}
	/*sort(e+1,e+1+m);
	for(re int i=1;i<=m;++i){
		if(basea<e[i].x){
			basea=e[i].x;
			baseb=0;
		}
		if(baseb<e[i].y){
			//printf("x=%d y=%d\n",e[i].x,e[i].y);
			add(e[i].x,e[i].y);
			add(e[i].y,e[i].x);
			++inn[e[i].x];
			++inn[e[i].y];
			baseb=e[i].y;
		}
	}*/

	toposort();
	for(re int i=1;i<=n;++i){
		if(!check[i]){
			//printf("%d ",i);
			ans=ans xor i;
		}
	}
	printf("%d\n",ans);
	return 0;
}
/*
6 15
1 2
2 1
1 3
3 1
1 4
2 3
3 2
2 4
4 2
3 4
3 4
5 2
5 3
5 6
6 2
*/

/*
5
18
1 2
1 3
2 5
5 4
5 3
3 4
2 4
2 3
3 5
1 3
4 3
2 4
5 2
1 2
3 1
4 3
5 2
4 5
*/