void Insert(forward_list<string> &lst, const string &str1, const string &str2) {
auto prev = lst.cbefore_begin();
auto curr = lst.cbegin();
while (curr != lst.cend()) {
if (*curr != str1) {
prev = curr;
++curr;
}
else {
lst.insert_after(curr, str2);
return;
}
}
lst.insert_after(prev, str2);
}
