include

include

using namespace std;

int main()
{
int t;
cin >> t;
while (t--)
{
int n;
cin >> n;
vector a(n), b(n + 1), c(n + 1);

    for (int i = n - 1; i >= 0; i--)
    {
        char c;
        cin >> c;
        a[i] = c - '0';
    }

   
    if (a[n - 1] == 9)
    {
        for (int i = 0; i <= n; ++i)
        {
            b[i] = 1;
        }
    }
    else
    {
        for (int i = 0; i < n; ++i)
        {
            b[i] = 9;
        }
    }

    for (int i = 0; i < n; i++)
    {
        if (b[i] < a[i])
        {
            b[i + 1]--;
            b[i] += 10;
        }
        c[i] = b[i] - a[i];
    }


    for (int i = n - 1; i >= 0; i--)
    {
        cout << c[i];
    }
    cout << '\n';
}
return 0;

}