I'm doing some exam prep for my discrete mathematics course, and I have to implement the function

f(x) = ((9^x)-2)%5

Since the values of our x in the assignment is 100000 < x <= 1000000, I'm having some trouble handling the overflow

In our assignment there's a hint: "Find a way to apply the modulus throughout the calculations. Otherwise you will get much too big numbers very quickly when calculating 9^x"

I cannot figure out the logic to make this work tho, any help would be appreciated

/* This function should return 1 if 9^x-2 mod 5 = 2 and 0 otherwise */
int is2mod5(int x){
    int a;
    double b = pow(9, x);
    a = b;
    int c = (a-2)%5;

    if (c == 2)
    {
        return 1;
    }
    else
    {
        return 0;
    }
}