foo.c:1:9: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘<’ token
    1 | include <iostream>
      |         ^
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:8:16: error: implicit declaration of function ‘swap’ [-Wimplicit-function-declaration]
    8 |         if(a<c)swap(a,c);
      |                ^~~~
foo.c:11:9: error: ‘cout’ undeclared (first use in this function)
   11 |         cout<<b<<' '<<a;
      |         ^~~~