/in/foo.cc: In function 'int main()':
/in/foo.cc:8:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<n;++i)
              ~^~
/in/foo.cc:14:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=a[0]>0? a[0]:1;i<=a[n-1];++i)
                           ~^~~~~~~~