View Compilation Error

0_0_38762168_29271.cpp:11:16: error: expected unqualified-id before ')' token
   11 |     Fenwick<T>() {}
      |                ^
0_0_38762168_29271.cpp:12:16: error: expected unqualified-id before 'int'
   12 |     Fenwick<T>(int _n) : n(_n), t(_n + 1) {}
      |                ^~~
0_0_38762168_29271.cpp:12:16: error: expected ')' before 'int'
   12 |     Fenwick<T>(int _n) : n(_n), t(_n + 1) {}
      |               ~^~~
      |                )
0_0_38762168_29271.cpp:13:16: error: expected unqualified-id before 'int'
   13 |     Fenwick<T>(int _n, T *a) : n(_n) {
      |                ^~~
0_0_38762168_29271.cpp:13:16: error: expected ')' before 'int'
   13 |     Fenwick<T>(int _n, T *a) : n(_n) {
      |               ~^~~
      |                )