/in/foo.c: In function 'main':
/in/foo.c:7:5: error: 'i' undeclared (first use in this function)
 for(i=1;i<=n;i++){
     ^
/in/foo.c:7:5: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:9:2: error: expected ';' before '}' token
  }
  ^
/in/foo.c:11:2: error: 'retrun' undeclared (first use in this function)
  retrun 0;
  ^~~~~~
/in/foo.c:11:9: error: expected ';' before numeric constant
  retrun 0;
         ^