/in/foo.cc: In function 'void dfs(int, int)':
/in/foo.cc:52:9: warning: unused variable 'i' [-Wunused-variable]
   52 |     int i, j;
      |         ^
/in/foo.cc:52:12: warning: unused variable 'j' [-Wunused-variable]
   52 |     int i, j;
      |            ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:74:15: warning: unused variable 'x' [-Wunused-variable]
   74 |     int i, j, x, y;
      |               ^
/in/foo.cc:74:18: warning: unused variable 'y' [-Wunused-variable]
   74 |     int i, j, x, y;
      |                  ^
/in/foo.cc:75:10: warning: unused variable 'ch' [-Wunused-variable]
   75 |     char ch;
      |          ^~