/in/foo.cc: In function 'int main()':
/in/foo.cc:17:33: warning: 'b' may be used uninitialized in this function [-Wmaybe-uninitialized]
  cout<<m<<" "<<n<<" "<<a<<" "<<b;
                                 ^
/in/foo.cc:17:27: warning: 'a' may be used uninitialized in this function [-Wmaybe-uninitialized]
  cout<<m<<" "<<n<<" "<<a<<" "<<b;
                           ^~~