Explain the Error in the Following Code

Explain the error in the following code.You may give the warning message,or error message,your compiler might give for the following error,or you may describe the error.However you present the error,you must explain clearly what is wrong.
#include <iostream>
//Test question
void show_array(int ar[],int size)
{
using namespace std;
for(int i = 0;i < size;i++)
cout << ar[i] << " ";
cout << endl;
}
int main()
{
const int a[6] = {2,4,2,3,5};
show_array(a,6);
//...
}