HIIT remains

#include <iostream>
#include <cstring>

using namespace std;

int main() {
	int t;
	cin >> t;
	const char target[] = "HIIT";
	long long int arr[20000*4];
	for (int tt = 0; tt < t; tt++) {
		string s;
		cin >> s;
		for (int j = 0; j < 4; j++) {
			arr[j] = 0;
		}
		if (s[0] == target[0])
			arr[0] = 1;
		for (int i = 1; i < (int)s.size(); i++) {
			for (int j = 0; j < 4; j++) {
				arr[i*4+j] = arr[(i-1)*4+j];
			}
			for (int j = 0; j < 4; j++) {
				if (s[i] != target[j])
					continue;
				if (j == 0) {
					arr[i*4+j] += 1;
				} else {
					arr[i*4+j] += arr[(i-1)*4+j-1];
				}
			}
		}
		cout << arr[(s.size()-1)*4+3] << endl;
	}
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: RUNTIME ERROR

Test 4

Verdict: RUNTIME ERROR