foo.c: In function ‘main’:
foo.c:3:9: error: ‘cin’ undeclared (first use in this function)
    3 |         cin>>a>>b>>c;
      |         ^~~
foo.c:3:9: note: each undeclared identifier is reported only once for each function it appears in
foo.c:19:5: error: ‘cout’ undeclared (first use in this function)
   19 |     cout<<a<<" "<<b<<" "<<c；
      |     ^~~~
foo.c:19:27: error: ‘c；’ undeclared (first use in this function)
   19 |     cout<<a<<" "<<b<<" "<<c；
      |                           ^~~
foo.c:19:30: error: expected ‘;’ at end of input
   19 |     cout<<a<<" "<<b<<" "<<c；
      |                              ^
      |                              ;
foo.c:19:5: error: expected declaration or statement at end of input
   19 |     cout<<a<<" "<<b<<" "<<c；
      |     ^~~~