Environment dependent characters? are displayed.

test values
Input:
xyz
abc

Correct output: xaybzc

current output value
xaybzc �

#include<bits/stdc++.h>

using namespace std;

int main() {
    stringo,e;
    cin>>o>>e;
    
    US>//#stringans=";
    int index = 0;
    for(inti=1;i<=o.size()+e.size();i++){
        an.push_back(o[index]);
        an.push_back(e[index]);
        index++;
    }
    
    cout<ans<<endl;

    return 0;
}