private async void upisiRezulat_Click(object sender, RoutedEventArgs e)
        {
            if (imeIPrezime.Text == "")
                obavestenje.Text = "Potrebno je da unesete ime i prezime.";
            else
            {
                string podatak = imeIPrezime.Text + "\n";

                StorageFolder folder = ApplicationData.Current.LocalFolder;
                StorageFile sampleFile = await folder.CreateFileAsync("rekordi.txt", CreationCollisionOption.OpenIfExists );
                await FileIO.WriteTextAsync(sampleFile, podatak);

            }
        }