#include<iostream>
#include<vector>
#include<string>
using namespace std;

struct graph{
  int nedges;
  int nvertices;
  vector < vector<int> > edges;
  vector<bool> visited;
  vector<string> color;
};

void create_graph(struct graph &g, int nedges, int nvertices);

int color(struct graph &g, int v, string hue);

int flag;

int main()
{
  int edges,vertices;

  flag = 0;

  while(1)
    {
      cin >> vertices;

      if(vertices==0) break;

      cin>>edges;

      graph *g = new graph;
      
      create_graph(*g,edges,vertices);

      color(*g,0,"blue");

      if(flag==1) cout<<"NOT BICOLORABLE"<<endl;
      else cout<<"BICOLORABLE"<<endl;
      flag=0;
 
      delete g;
    }


  return(0);
}


void create_graph(struct graph &g, int nedges, int nvertices)
{
  int i,j,n1,n2;

  g.nedges = nedges;
  g.nvertices = nvertices;
  g.edges.resize(nvertices);
  g.visited.resize(nvertices);
  g.color.resize(nvertices);

  for(i=0;i<nedges;i++)
    {
      cin>>n1>>n2;

      g.edges[n1].push_back(n2);
      g.edges[n2].push_back(n1);

    }

  for(i=0;i<g.nvertices;i++) g.visited[i] = false;
}


int color(struct graph &g, int v, string hue)
{
  int i;
  string child_color = hue;

  //not yet colored, so color it
  if(!g.visited[v])
    {
      g.color[v] = child_color;
      if(g.color[v]=="blue") child_color = "red";
      else child_color = "blue";
      g.visited[v] = true;
      for(i=0;i<g.edges[v].size();i++) color(g,g.edges[v][i],child_color);
    }

  //already colored
  else if(g.color[v] != child_color) flag=1;

}