/in/foo.c: In function 'main':
/in/foo.c:28:12: error: 'max' undeclared (first use in this function)
  wang(a,10,max,min,ag);
            ^~~
/in/foo.c:28:12: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:28:16: error: 'min' undeclared (first use in this function)
  wang(a,10,max,min,ag);
                ^~~
/in/foo.c:28:20: error: 'ag' undeclared (first use in this function)
  wang(a,10,max,min,ag);
                    ^~