/in/foo.cc: In function 'int main()':
/in/foo.cc:43:9: warning: unused variable 'u' [-Wunused-variable]
     int u=find(i),v=find(j);
         ^
/in/foo.cc:43:19: warning: unused variable 'v' [-Wunused-variable]
     int u=find(i),v=find(j);
                   ^
/in/foo.cc:24:6: warning: 'n' may be used uninitialized in this function [-Wmaybe-uninitialized]
  int n,top,back,h;
      ^