/in/foo.cc: In function 'bool check(int, int)':
/in/foo.cc:9:6: warning: comparisons like 'X<=Y<=Z' do not have their mathematical meaning [-Wparentheses]
  if(1<=x<=n&&1<=y<=n&&x!=y) return true;
     ~^~~
/in/foo.cc:9:15: warning: comparisons like 'X<=Y<=Z' do not have their mathematical meaning [-Wparentheses]
  if(1<=x<=n&&1<=y<=n&&x!=y) return true;
              ~^~~
/in/foo.cc: In function 'void dfs(int, int)':
/in/foo.cc:29:7: warning: left operand of comma operator has no effect [-Wunused-value]
  if(tx>n,ty>n)
     ~~^~
/in/foo.cc: In function 'bool checktwo(int, int)':
/in/foo.cc:26:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^