/in/foo.c: In function 'main':
/in/foo.c:6:4: warning: left-hand operand of comma expression has no effect [-Wunused-value]
  (a,b)==n;
    ^
/in/foo.c:6:7: warning: statement with no effect [-Wunused-value]
  (a,b)==n;
  ~~~~~^~~
/in/foo.c:7:6: warning: comparison of constant '100000' with boolean expression is always true [-Wbool-compare]
  1<=n<=100000;
      ^~
/in/foo.c:7:3: warning: comparisons like 'X<=Y<=Z' do not have their mathematical meaning [-Wparentheses]
  1<=n<=100000;
  ~^~~
/in/foo.c:7:2: warning: statement with no effect [-Wunused-value]
  1<=n<=100000;
  ^
/in/foo.c:8:2: error: 'cout' undeclared (first use in this function)
  cout<<n<<endl;
  ^~~~
/in/foo.c:8:2: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:8:11: error: 'endl' undeclared (first use in this function)
  cout<<n<<endl;
           ^~~~