int n, i;
bool flag = false;

cout << "Enter a positive  integer: ";
cin >> n;

for(i = 2; i <= n/2; ++i)
{
    if (checkPrime(i))
    {
        if (checkPrime(n - i))
        {
            cout << n << " = " << i << " + " << n-i << endl;
            flag = true;
        }
    }
}

if (!flag)
  cout << n << " can't be expressed as sum of two prime numbers.";

return 0;

bool isPrime = true;

for(i = 2; i <= n/2; ++i)
{
    if(n % i == 0)
    {
        isPrime = false;
        break;
    }
}

return isPrime;