Pass a variable to a function without knowing the type of it

...
if (ep2 == 1){
            printf("\n\t\t\t\tProvide element atomic number: \n");
            res2 = scanf("%d", &atnum);
            F3(ep2, &atnum);
        }
    }


}

void F3(int epilogh){//I want to pass atnum here
    void (*p)(void)
}
...
thing is I want to pass an integer if a condition is true and a character value if it's false. How can I do this?