foo.cc: In function ‘bool check(int, int)’:
foo.cc:9:13: warning: comparisons like ‘X<=Y<=Z’ do not have their mathematical meaning [-Wparentheses]
    9 |         if(1<=x<=n&&1<=y<=n&&x!=y) return true;
      |            ~^~~
foo.cc:9:22: warning: comparisons like ‘X<=Y<=Z’ do not have their mathematical meaning [-Wparentheses]
    9 |         if(1<=x<=n&&1<=y<=n&&x!=y) return true;
      |                     ~^~~
foo.cc: In function ‘void dfs(int, int)’:
foo.cc:29:14: warning: left operand of comma operator has no effect [-Wunused-value]
   29 |         if(tx>n,ty>n)
      |            ~~^~
foo.cc: In function ‘bool checktwo(int, int)’:
foo.cc:26:1: warning: control reaches end of non-void function [-Wreturn-type]
   26 | }
      | ^