func_code_string: #include <bits/stdc++.h>   using namespace std;   int n, m, i, d[100005], x, y, a, b, c, r;   int main() {     cin >> n >> m;     for (i = 1; i <= m; i++) {       cin >> x >> y;       d[x]++;       d[y]++;     }     for (i = 1; i <= n; i++) {       if (d[i] == 1) a++;       if (d[i] == 2) b++;       if (d[i] == n - 1)         c++;       else         r++;     }     if (a == 2 && b == n - 2) {       cout <<  bus topology ;       return 0;     }     if (a == n - 1 && c == 1) {       cout <<  star topology ;       return 0;     }     if (b == n) {       cout <<  ring topology ;       return 0;     }     cout <<  unknown topology ;     return 0;   }   