View Compilation Error

0_0_21047004_28239.cpp: In function 'int build(int, int)':
0_0_21047004_28239.cpp:32:62: error: 'P' was not declared in this scope
   T[data].num=(T[T[data].pl].num*f[r-mid]+T[T[data].pr].num)%P;
                                                              ^
0_0_21047004_28239.cpp: In function 'long long int gethash(int, int, int)':
0_0_21047004_28239.cpp:41:71: error: 'P' was not declared in this scope
  return (gethash(pl,mid,T[x].pl)*f[pr-mid]+gethash(mid+1,pr,T[x].pr))%P;
                                                                       ^
0_0_21047004_28239.cpp: In function 'void change(int, int, char)':
0_0_21047004_28239.cpp:50:57: error: 'P' was not declared in this scope
  T[x].num=(T[T[x].pl].num*f[T[x].r-mid]+T[T[x].pr].num)%P;
                                                         ^
0_0_21047004_28239.cpp: In function 'int main()':
0_0_21047004_28239.cpp:69:19: error: 'P' was not declared in this scope
    f[i]=f[i-1]*27%P;
                   ^