answer.code:13:1: error: ‘unordered_map’ does not name a type
   13 | unordered_map<double, int> um;
      | ^~~~~~~~~~~~~
answer.code: In function ‘void dfs(double, double, long long int)’:
answer.code:17:13: error: ‘um’ was not declared in this scope; did you mean ‘tm’?
   17 |         if (um[a] > 0) return;
      |             ^~
      |             tm
answer.code:24:9: error: ‘um’ was not declared in this scope; did you mean ‘tm’?
   24 |         um[a * 0.5] = 1;
      |         ^~
      |         tm