foo.cc: In function 'void make_tree(int, int, int)':
foo.cc:22:15: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   make_tree((l+r>>1)+1,r,(x<<1)+1); 
               ^
foo.cc: In function 'int main()':
foo.cc:65:14: warning: unused variable 'j' [-Wunused-variable]
  int n,m,k,i,j,l,r,x,ans,t1,t2;
              ^
foo.cc:65:29: warning: unused variable 't2' [-Wunused-variable]
  int n,m,k,i,j,l,r,x,ans,t1,t2;
                             ^