<?php

// read number of test cases
fscanf(STDIN, "%d\n", $t);

// loop through test cases
for ($i = 1; $i <= $t; $i++) {
    // read input
    fscanf(STDIN, "%d\n", $n);
    $colors = explode(' ', trim(fgets(STDIN)));

    // determine unique colors
    $unique_colors = array_unique($colors);

    // check if it's impossible to label the cards
    if (count($unique_colors) > $n) {
        echo "Case #$i: IMPOSSIBLE\n";
        continue;
    }

    // sort unique colors
    sort($unique_colors);

    // assign labels to colors
    $label = 1;
    $color_labels = [];
    foreach ($unique_colors as $color) {
        $color_labels[$color] = $label++;
    }

    // output result
    $output = [];
    foreach ($colors as $color) {
        $output[] = $color_labels[$color];
    }
    echo "Case #$i: " . implode(' ', $output) . "\n";
}