Why am I always getting 1 as answer irrespective of the value assigned to the variable a

Why am I getting 1 as output instead of 7 ( if a is initially assigned with 12 , then a-5 should give 7) or 3 as ( if a is assigned with 8 then a-5 should give 3 ). The output remains 1 always irrespective of the value assigned to a.

int main()
{
    int a = 12;
    if (a = 8  && (a = a - 5))
        cout << a;
    else
    {
        //do nothing !!
    }
}