8

#include <iostream>
#include <vector>
#include <unordered_set>
using namespace std;

bool hasArithmeticSubsequence(const vector<int>& arr) {
int n = arr.size();
if (n < 3) return false;

for (int j = 1; j < n - 1; ++j) {
    unordered_set<int> left;
    for (int i = 0; i < j; ++i) {
        left.insert(arr[i]);
    }
    for (int k = j + 1; k < n; ++k) {
        int required = 2 * arr[j] - arr[k];
        if (left.count(required)) {
            return true;
        }
    }
}
return false;

}

int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);

int T;
cin >> T;
while (T--) {
    int N;
    cin >> N;
    vector<int> arr(N);
    for (int i = 0; i < N; ++i) {
        cin >> arr[i];
    }
    if (hasArithmeticSubsequence(arr)) {
        cout << "Y\n";
    } else {
        cout << "N\n";
    }
}

return 0;

}