How can I print the variable that a void pointer points to

I would like the function to return different types depending on different parameter values, but how can I print the variable the void pointer points to in main()?

#include <iostream>
#include <string>
using namespace std;
void * func(int a)
{
     if (a == 1)
     {
     int param = 5;
     return &param;
     }
     else if (a == 2)
    {
    double param = 5.5;
    return &param;
    }
    else if (a == 3)
    {
    string param = "hello";
    return &param;
    }
    else
    {
    return nullptr;
    }
}
int main()
{

    void *ptr = func(3);//

    cout << ptr;// print the address not the value
    getchar();
    return 0;
 }