/in/foo.c: In function 'main':
/in/foo.c:6:3: error: 'sum' undeclared (first use in this function)
    6 |   sum
      |   ^~~
/in/foo.c:6:3: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:6:6: error: expected ';' at end of input
    6 |   sum
      |      ^
      |      ;
/in/foo.c:6:3: error: expected declaration or statement at end of input
    6 |   sum
      |   ^~~
/in/foo.c:4:7: warning: unused variable 'i' [-Wunused-variable]
    4 | { int i,n;
      |       ^