/in/foo.cc: In function 'int main()':
/in/foo.cc:43:23: warning: format '%lf' expects argument of type 'double', but argument 2 has type 'long double' [-Wformat=]
  printf("%0.2lf\n",ans);
                       ^
/in/foo.cc:42:17: warning: 'len' may be used uninitialized in this function [-Wmaybe-uninitialized]
  ans=work(0,len);
                 ^