View Compilation Error

0_0_19294306_23727.cpp: In function 'int main()':
0_0_19294306_23727.cpp:61:49: error: 'M_PI' was not declared in this scope
             printf("%d\n",(int)(0.5 * log10(2 * M_PI * n) + n * log10(n * 1.0 / M_E) + 1));
                                                 ^
0_0_19294306_23727.cpp:61:81: error: 'M_E' was not declared in this scope
             printf("%d\n",(int)(0.5 * log10(2 * M_PI * n) + n * log10(n * 1.0 / M_E) + 1));
                                                                                 ^