---

Lỗi biên dịch:

Main.cc: In function ‘int main()’:
Main.cc:23:9: error: ‘n’ was not declared in this scope
     if (n < 0 || n > 5000) {
         ^
Main.cc:27:24: error: ‘n’ was not declared in this scope
     double kq = tinhPi(n);
                        ^
Main.cc:21:10: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d", &a);
     ~~~~~^~~~~~~~~~