/in/foo.cc: In function 'int main()':
/in/foo.cc:19:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=1;i<=n;i++){
              ~^~~
/in/foo.cc:30:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=1;i<=n;i++){
              ~^~~
/in/foo.cc:28:6: warning: unused variable 'fir' [-Wunused-variable]
  int fir=1;
      ^~~