View Compilation Error

0_0_16983681_27825.cpp: In function 'int stelin(int)':
0_0_16983681_27825.cpp:6:30: error: 'log' was not declared in this scope
  return (int) ceil((n * log(n) - n + 0.5 * log( 2 * n * 3.141592653)) / log(10));
                              ^
0_0_16983681_27825.cpp:6:80: error: 'ceil' was not declared in this scope
  return (int) ceil((n * log(n) - n + 0.5 * log( 2 * n * 3.141592653)) / log(10));
                                                                                ^