Queue Using two Stacks

#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
#include <stack>
using namespace std;
void tranfer(stack <long> &from,stack <long> &to){
    while(!from.empty()){
        to.push(from.top());
        from.pop();
    }
}

int main() {
    stack <long> s,ss;
    int i,option,q;
     long data,temp;
    cin>>q;
    while(q--)
    {   
        cin>>option;
        if(option==1){
            cin>>data;
            s.push(data);
        }
        else if (option==2){
            if(ss.empty()){tranfer(s,ss);}
            ss.pop();
        }
        else{  
        if(ss.empty()){tranfer(s,ss);}
        cout<<ss.top()<<endl;
        }
    }
    return 0;
    }