HIIT Generation

#include <bits/stdc++.h>
#include <string>
#include <vector>
#include <list>
 
using namespace std;
 
 
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
 
list <char> r;
r.push_back('H');
r.push_back('I');
r.push_back('I');
r.push_back('T');
 
int n;
cin >> n;
char a;
 
 
for (int i=0; i<n; i++) {
    cin >> a;
     
    for (list<char>::iterator it=r.begin(); it!=r.end(); ++it) {
        if (*it == a) {
            *it = 'T';
            r.insert(it, 'H');++it;
            r.insert(it, 'I');++it;
            r.insert(it, 'I');
            ++it;                  
        }
    }
}
    for (list<char>::iterator it=r.begin(); it!=r.end(); ++it) { 
        cout << *it;
}
}

Test 1

Verdict: TIME LIMIT EXCEEDED

Test 2

Verdict: TIME LIMIT EXCEEDED

Test 3

Verdict: WRONG ANSWER

Test 4

Verdict: ACCEPTED