HIIT Generation

#include <bits/stdc++.h>

using namespace std;

int n; 
char m[1000];

string expand(string c, int i){
    if(i == n)
        return c;
    
    if(c[0] == m[i]){
        return expand("H", i+1)+expand("I", i+1)+expand("I", i+1)+expand("T", i+1);
    }
    else
        return expand(c, i+1);
}

int main(){
    cin >> n;
    for(int i = 0; i < n; ++i){
        cin >> m[i];
    }
    cout << expand("H", 0)+expand("I", 0)+expand("I", 0)+expand("T", 0) << endl;
    return 0;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: RUNTIME ERROR

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED