View Compilation Error

0_0_14251826_12384.cpp: In function 'E ask(int, int, int, int, int)':
0_0_14251826_12384.cpp:74:55: error: invalid initialization of non-const reference of type 'E&' from an rvalue of type 'E'
       if(L <= m)  e = up(e , ask(L , R , l , m , t<<1)) ;
                                                       ^
0_0_14251826_12384.cpp:24:6: note: in passing argument 2 of 'E up(E&, E&)'
 E    up(E &l , E &r){
      ^
0_0_14251826_12384.cpp:75:60: error: invalid initialization of non-const reference of type 'E&' from an rvalue of type 'E'
       if(R > m)    e = up(e , ask(L , R , m+1 , r , t<<1|1)) ;
                                                            ^
0_0_14251826_12384.cpp:24:6: note: in passing argument 2 of 'E up(E&, E&)'
 E    up(E &l , E &r){
      ^