/in/foo.cc: In function 'int main()':
/in/foo.cc:93:20: warning: unused variable 'u' [-Wunused-variable]
   93 |     for(int i = 1, u, v, w; i <= m; i++) {
      |                    ^
/in/foo.cc:93:23: warning: unused variable 'v' [-Wunused-variable]
   93 |     for(int i = 1, u, v, w; i <= m; i++) {
      |                       ^
/in/foo.cc:93:26: warning: unused variable 'w' [-Wunused-variable]
   93 |     for(int i = 1, u, v, w; i <= m; i++) {
      |                          ^

FileNotFoundError('input/ex_tree2.in')