https://codeforces.com/contest/1974/problem/D

#include <bits/stdc++.h>
using namespace std;
#define int long long
typedef pair<int, int> PII;
typedef vector<int> VI;
typedef vector<VI> VVI;
#define rep(i,a,n) for (int i=a;i<=n;i++)
#define per(i,a,n) for (int i=a;i>=n;i--)
#define oz 998244353
#define N 200010
#define INF 0x3f3f3f3f
typedef long long ll;
#define endl '\n'
const int mod = 1e9 + 7;


int ch[500];
void solve() {
    int n;
    cin >> n;

    vector<char> res;

    string s;
    cin >> s;

    int ok = 0;
    ch['W'] = ch['E'] = 1;
    ch['N'] = ch['S'] = 0;

    for (int i = 0; i < n; i++) {

        if (!ch[s[i]]) {
            res.push_back('R');
            ok |= 1;
        }

        else {
            res.push_back('H');
            ok |= 2;
        }

        ch[s[i]] ^= 1;
    }

    if (ok == 3 && ch['W'] == ch['E'] && ch['N'] == ch['S']) {
        for (auto t : res)cout << t;
        cout << endl;

    }

    else cout << "NO" << endl;


}

signed main() {

    ios::sync_with_stdio(false);
    cin.tie(0), cout.tie(0);

    int T = 1;
    cin >> T;
    while (T --)

        solve();

    return 0;
}