foo.c: In function ‘main’:
foo.c:7:9: error: ‘cin’ undeclared (first use in this function)
    7 |         cin>>a>>b>>c;
      |         ^~~
foo.c:7:9: note: each undeclared identifier is reported only once for each function it appears in
foo.c:8:23: error: ‘cout’ undeclared (first use in this function)
    8 |         if(a>b&&b>c)  cout<<a<<""<<b<<""<<c<<end1;//
      |                       ^~~~
foo.c:8:46: error: ‘end1’ undeclared (first use in this function)
    8 |         if(a>b&&b>c)  cout<<a<<""<<b<<""<<c<<end1;//
      |                                              ^~~~