/in/foo.cc: In function 'void work()':
/in/foo.cc:103:8: warning: unused variable 't' [-Wunused-variable]
    int t=lca(x,y);
        ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:111:6: warning: unused variable 'x' [-Wunused-variable]
  int x,y,i,j; 
      ^
/in/foo.cc:111:8: warning: unused variable 'y' [-Wunused-variable]
  int x,y,i,j; 
        ^