C++ implementation Stack added overloading(int,string) (there is no optimization yet)

#include <iostream>
using namespace std;
struct Element{
    int data=0;
    string data2;
    string nazwa;
    Element* under=NULL;
};
void pushint(int d,Element* &top){
    Element* newobject = new Element;
    newobject->data=d;
    newobject->under=top;
    newobject->nazwa="int";
    top=newobject;
}
void pushstring(string d,Element* &top){
    Element* newobject = new Element;
    newobject->data2=d;
    newobject->under=top;
    newobject->nazwa="str";
    top=newobject;
}
void pop(Element* &top){
    if(top==NULL)exit(0);
    Element* temp = top;
    top=top->under;
    delete temp;
}
void show(Element* top){
    while(top!=NULL){
            if(top->nazwa == "int"){
                cout << top->data << " -> ";
            }else if(top->nazwa == "str"){
                cout << top->data2 << " -> ";
            }
        top=top->under;
    }cout <<"NULL";
}
int main(){
    Element* mystack = NULL;
    pushint(24,mystack);
    pushint(33,mystack);
    pushstring("hello",mystack);
    pushint(55,mystack);
    pushstring("omg",mystack);
    pushstring("lol",mystack);
    pushstring("wtf",mystack);
    pushint(6666,mystack);
    pushint(6666,mystack);
    show(mystack);
    cout<<endl<<endl;
    pop(mystack);
    pop(mystack);
    pop(mystack);
    show(mystack);
    cout<<endl;
    show(mystack);
// here you can check your ram
/*
    for(int i=0;i<3000000;i++){
        pushint(66,mystack);
        pushstring("helo",mystack);
    }
    int wait=0;
    cin >> wait;
    for(int i=0;i<1200000;i++){
        pop(mystack);
    }
*/
    return 0;
}