A - Blackboard List

#include <bits/stdc++.h>

using namespace std;

#define ll     long long
#define _test   int _TEST; cin>>_TEST; while(_TEST--)
#define pb     push_back
#define ppb    pop_back

int main()
{
    _test
    {
        int n;
        cin>>n;

        vector<ll int> a(n);
        for(auto &e: a)
            cin>>e;

        sort(a.begin(), a.end());

        if(a[0] >= 0)
            cout<<a[n-1]<<"\n";
        else
            cout<<a[0]<<"\n";
    }
}