code.cpp:12:40: error: expected unqualified-id before numeric constant
   12 |                                      ((2*x <= j && j < 3*x) && (0 <= i && i < x))
      |                                        ^
code.cpp:12:40: error: expected ')' before numeric constant
   12 |                                      ((2*x <= j && j < 3*x) && (0 <= i && i < x))
      |                                       ~^
      |                                        )
code.cpp:12:40: error: expected ')' before numeric constant
   12 |                                      ((2*x <= j && j < 3*x) && (0 <= i && i < x))
      |                                      ~ ^
      |                                        )