Mã chấm: 20121

Main.cc: In function ‘int main()’:
Main.cc:31:14: error: ‘b’ was not declared in this scope
  printf("%d",b);
              ^
Main.cc:4:7: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&n);
  ~~~~~^~~~~~~~~
Main.cc:7:8: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d",&a[i]);
   ~~~~~^~~~~~~~~~~~