/in/foo.c: In function 'main':
/in/foo.c:7:8: error: 'cin' undeclared (first use in this function)
    7 |  while(cin>>a>>b){
      |        ^~~
/in/foo.c:7:8: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:10:4: error: 'cout' undeclared (first use in this function)
   10 |    cout<<" ";
      |    ^~~~
/in/foo.c:15:9: error: 'endl' undeclared (first use in this function)
   15 |   cout<<endl:
      |         ^~~~
/in/foo.c:15:13: error: expected ';' before ':' token
   15 |   cout<<endl:
      |             ^
      |             ;