#include<iostream>
#include<cstdio>
using namespace std;
int N[100010],M[500010],k,f,first=1,d[500010][3];
int n,m;
int main(){
	freopen("asm_game.in","r",stdin);
	freopen("asm_game.out","w",stdout);
	cin>>n>>m;
	for(int i=1;i<=m;i++){
		for(int j=1;j<=2;j++){
			cin>>d[i][j];
			N[d[i][j]]+=1;
		}
		
	}
	for(int i=1;i<=n;i++){
		if(N[i]<3)
		{
			for(int y=1;y<=m;y++)
			{			
			for(int h=1;h<=2;h++)
			{
				if(i==d[y][h])
				{
					if(h%2==0)
					N[d[y][h-1]]--;
					else
					N[d[y][h+1]]--;
				}
			}
			}
		}
	}
	for(int i=1;i<=n;i++){
		if(N[i]>2){
			if(first){first=0;f=i;}
			else
			f=f^i;
		}		
	}
	cout<<f;
	return 0;
}