View Compilation Error

0_0_39146928_13573.cpp: In function 'void st_create()':
0_0_39146928_13573.cpp:48:15: error: 'log2' was not declared in this scope
   48 |         int k=log2(n);
      |               ^~~~
0_0_39146928_13573.cpp: In function 'int LCA(int, int)':
0_0_39146928_13573.cpp:57:15: error: 'log2' was not declared in this scope
   57 |         int k=log2(n);
      |               ^~~~