Copying Stack

Copy All Elements of a Stack S1 into another Stack S2.

#include <iostream>
#include <stack>

using namespace std;

int main() {
    stack <int> S1;
    stack <int> S2;
    stack <int> temp;

    cout << "Enter the Stack Elements (-1 to stop):" << endl;

    int n;
    while(true) {
        cin >> n;
        if(n < 0) break;

        S1.push(n);
    }

    while(!S1.empty()) {
        temp.push(S1.top());
        S1.pop();
    }

    while(!temp.empty()) {
        S1.push(temp.top());
        S2.push(temp.top());
        temp.pop();
    }
    return 0;
}