#include<iostream>
#include<cstring>
#include<algorithm>
#include<cstdio>
#include<vector>
#include<sstream>
#include<string>
#include<climits>
#include<stack>
#include<set>
#include<bitset>
#include<cmath>
#include<deque>
#include<map>
#include<queue>
#define iinf 2000000000
#define linf 1000000000000000000LL
#define dinf 1e200
#define eps 1e-11
#define all(v) (v).begin(),(v).end()
#define sz(x) x.size()
#define pb push_back
#define mp make_pair
#define lng long long
#define sqr(a) ((a)*(a))
#define pii pair<int,int>
#define pll pair<lng,lng>
#define pss pair<string,string>
#define pdd pair<double,double>
#define X first
#define Y second
#define pi 3.14159265359
#define ff(i,xi,n) for(int i=xi;i<=(int)(n);++i)
#define ffd(i,xi,n) for(int i=xi;i>=(int)(n);--i)
#define ffl(i,r) for(int i=head[r];i!=-1;i=edge[i].next)
#define cc(i,j) memset(i,j,sizeof(i))
#define two(x) ((lng)1<<(x))
#define N 17000
#define M 1000000
#define lson l , mid , rt << 1
#define rson mid + 1 , r , rt << 1 | 1
#define Mod n
#define Pmod(x) (x%Mod+Mod)%Mod
using namespace std;
typedef vector<int> vi;
typedef vector<string> vs;
typedef unsigned int uint;
typedef unsigned lng ulng;
template<class T> inline void checkmax(T &x,T y){if(x<y) x=y;}
template<class T> inline void checkmin(T &x,T y){if(x>y) x=y;}
template<class T> inline T Min(T x,T y){return (x>y?y:x);}
template<class T> inline T Max(T x,T y){return (x<y?y:x);}
template<class T> T gcd(T a,T b){return (a%b)==0?b:gcd(b,a%b);}
template<class T> T lcm(T a,T b){return a*b/gcd(a,b);}
template<class T> T Abs(T a){return a>0?a:(-a);}
template<class T> inline T lowbit(T n){return (n^(n-1))&n;}
template<class T> inline int countbit(T n){return (n==0)?0:(1+countbit(n&(n-1)));}
template<class T> inline bool isPrimeNumber(T n)
{if(n<=1)return false;for (T i=2;i*i<=n;i++) if (n%i==0) return false;return true;}
template<class T> inline T Minmin(T a,T b,T c,T d){return Min(Min(a,b),Min(c,d));}
struct tarjan_seg
{
int head[N],tot,id[N],pre[N],low[N],stack[N],top,n,Index,nn,newid,newhead[N],*cur,contain[N];
struct pp
{
int v,next;
}edge[N*20];
void add(int u,int v)
{
edge[tot].v=v;
edge[tot].next=cur[u];
cur[u]=tot++;
}
void init()
{
cc(head,-1);
cc(newhead,-1);
tot=0;
newid=0;
cur=head;
cc(pre,-1);
cc(low,-1);
top=0;
cc(id,-1);
Index=0;
}
void tarjan(int r,int p)
{
bool xx=false;
pre[r]=low[r]=++Index;
stack[++top]=r;
ffl(i,r)
{
int v=edge[i].v;
if(v==p&&xx==0)
{
xx=1;
continue;
}
if(pre[v]==-1)
{
tarjan(v,r);
checkmin(low[r],low[v]);
}
else
if(id[v]==-1)
checkmin(low[r],pre[v]);
}
if(pre[r]==low[r])
{
int v;
++newid;
do
{
v=stack[top--];
id[v]=newid;
}while(v!=r);
}
}
void solve()
{
ff(i,1,n)
if(pre[i]==-1)
tarjan(i,-1);
}
void build_map()
{
int hash[N]={};
cur=newhead;
ff(i,1,n)
{
ffl(j,i)
{
int v=edge[j].v;
if(id[i]!=id[v]&&hash[id[i]]!=id[v])
add(id[v],id[i]),hash[id[i]]=id[v];
}
}
}
void solve_contain()
{
cc(contain,-1);
cur=contain;
ff(i,1,n)
add(id[i],i);
}
bool two_sat()
{
solve();
for(int i=1;i<=n;i+=2)
if(id[i]==id[i+1])
return false;
return true;
}
void dfs(int r)
{
pre[r]=++Index;
for(int i=newhead[r];i!=-1;i=edge[i].next)
if(pre[edge[i].v]==-1) dfs(edge[i].v);
low[++newid]=r;
}
void color_dfs(int r)
{
pre[r]=2;
for(int i=newhead[r];i!=-1;i=edge[i].next)
if(pre[edge[i].v]==-1) color_dfs(edge[i].v);
}
void Color()
{
cc(pre,-1);
for(int i=nn;i>0;--i)
if(pre[low[i]]==-1)
{
int a=edge[contain[low[i]]].v;
int b;
b=((a+1)/2)*4-1-a;
pre[low[i]]=1;
if(pre[id[b]]==-1)
color_dfs(id[b]);
}
}
void topo_sort()
{
nn=newid;
Index=0;
newid=0;
cc(pre,-1);
cc(low,-1);
ff(i,1,nn)
if(pre[i]==-1)
dfs(i);
}
void taganswer()
{
cc(low,-1);
ff(i,1,nn)
if(pre[i]==1) {
for(int j=contain[i];j!=-1;j=edge[j].next)
low[edge[j].v]=1;
}
}
void print_answer()
{
if(!two_sat())
{printf("NIE\n");
return ;
}
// printf("YES\n");
solve_contain();
build_map();
topo_sort();
Color();
taganswer();
ff(i,1,n)
{
if(low[i]==1)
{
printf("%d\n",i);
}
}
}
};
tarjan_seg G;
int na,m;
int main()
{
while(~scanf("%d%d",&na,&m))
{
G.n=2*na;
G.init();
ff(i,1,m)
{
int u,v;
scanf("%d%d",&u,&v);
G.add(u,(v+1)/2*4-1-v);
G.add(v,(u+1)/2*4-1-u);
}
G.print_answer();
}
return 0;
}
