Bicoloring

#include <algorithm>
#define push_back pb
#include <string>
#include <vector>
#include <iostream>
using namespace std;

vector<int> g[1005];

int colour[1005];
int visited[1005];

int a = -1;
bool wrong = 0;

void dfs(int a) {
    visited[a] = 1;
    for (int i=0; i < g[a].size(); i++) {
        if (visited[g[a][i]] == 0) {
            colour[g[a][i]] = 1 - colour[a];
            dfs(g[a][i]);
        }
        else {
            if (colour[g[a][i]] == colour[a]) {
                wrong = 1;
            }
        }
    }
}


int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    while (a != 0) {
        wrong = 0;
        for (int i=0; i < 1005; i++) {
            visited[i] = 0;
            colour[i] = 0;
        }

        cin >> a;
        if (a != 0) {
            int b;
            cin >> b;
            for (int i=1; i < a+1; i++) {
                g[i].clear();
            }

            for (int i=0; i<b; i++) {
                int x, y;
                cin >> x >> y;
                g[x].pb(y);
                g[y].pb(x);
            }

            dfs(1);
            if (wrong) {
                cout << "NOT BICOLOURABLE." << endl;
            }
            else {
                cout << "BICOLOURABLE." << endl;
            }
        }
    }

    return 0;
}