View Compilation Error

0_0_38897248_3733.cpp: In function 'void solve()':
0_0_38897248_3733.cpp:78:63: error: 'M_PI' was not declared in this scope; did you mean 'PI'?
   78 |                         if (angle_a <= PI / 2 && len_ca * sin(M_PI / 2 - angle_a) <= len) {
      |                                                               ^~~~
      |                                                               PI