View Compilation Error

0_0_37732699_8670.cpp: In member function 'void seg_tree::build(int, int, int)':
0_0_37732699_8670.cpp:77:31: error: 'len' was not declared in this scope
         l[rt] = L, r[rt] = R, len[rt] = R - L + 1, lazy[rt] = 0, is_clear[rt] = false;
                               ^