/in/foo.cc: In function 'int main()':
/in/foo.cc:41:12: warning: 'first' may be used uninitialized in this function [-Wmaybe-uninitialized]
  cnt=(first-1)+(n-last);
      ~~~~~~^~~
/in/foo.cc:41:18: warning: 'last' may be used uninitialized in this function [-Wmaybe-uninitialized]
  cnt=(first-1)+(n-last);
                ~~^~~~~~