#include <bits/stdc++.h>   using namespace std;   int n, m;   int in[100000 + 5];   bool doit() {     if (scanf( %d%d , &n, &m) != 2) return false;     for (int i = 0; i < n; ++i) in[i] = 0;     int x, y;     for (int i = 0; i < m; ++i) {       scanf( %d%d , &x, &y);       ++in[--x], ++in[--y];     }     sort(in, in + n);     if (in[0] == 1 && in[n - 2] == 1 && in[n - 1] == n - 1)       printf( star topology n );     else if (in[2] == 2 && in[n - 1] == 2) {       if (in[0] == 1 && in[1] == 1)         printf( bus topology n );       else if (in[0] == 2)         printf( ring topology n );       else         printf( unknown topology n );     } else       printf( unknown topology n );     return true;   }   int main() {     while (1)       if (!doit()) break;   }   