#define PI 3.14159

int main(void) {
  
  const double pi = 3.14159, e =  2.71828;

  pi = pi + 1;   // compile time error:
                 // assignment of read-only variable 'pi'

  e = e - 1;     // compile time error:
                 // assignment of read-only variable 'e'

  PI = 4.0;      // compile time error:
                 // lvalue required as left operand of assignment

  return 0;
}